Digital Dictionary

 General Computer Terminology

 Connectivity & Networking Terminology

 Internet Terminology

 Television Terminology

Notes on Sources Terminology

General Computer Terminology 

Back-End:  Front-end and back-end are terms used to characterize program interfaces and services relative to the initial user of these interfaces and services. (The "user" may be a human being or a program.) A "front-end" application is one that users interact with directly. A "back-end" application or program serves indirectly in support of the front-end services, usually by being closer to the required resource or having the capability to communicate with the required resource. The back-end application may interact directly with the front-end or, perhaps more typically, is a program called from an intermediate program that mediates front-end and back-end activities. A  front-end application might interface directly with users and forward requests to a remotely-located back-end program in another computer to get requested data or perform a requested service. Relative to the client/server computing model, a front-end is likely to be a client and a back-end to be a server. (1) 

Beta test:  In software and Web development, a beta test is the second phase of testing in which a sampling of the intended audience tries the product out. (Beta is the second letter of the Greek alphabet.) Originally, the term alpha test meant the first phase of testing in a software development process. The first phase includes unit testing, component testing, and system testing. Beta testing can be considered "pre-release testing." Beta test versions of software are now distributed to a wide audience on the Web partly to give the program a "real-world" test and partly to provide a preview of the next release. (1) 

CD:  A compact disc [sometimes spelled disk] (CD) is a small, portable, round medium made of molded polymer (close in size to the floppy disk) for electronically recording, storing, and playing back audio, video, text, and other information in digital form. Tape cartridges and CDs generally replaced the phonograph record for playing back music. At home, CDs have tended to replace the tape cartridge although the latter is still widely used in cars and portable playback devices. 

Initially, CDs were read-only, but newer technology allows users to record as well. CDs will probably continue to be popular for music recording and playback. A newer technology, the digital versatile disc (DVD), stores much more in the same space and is used for playing back movies.  (1)

Data Structure:  A data structure is a specialized format for organizing and storing data. General data structure types include the array, the file, the record, the table, the tree, and so on. Any data structure is designed to organize data to suit a specific purpose so that it can be accessed and worked with in appropriate ways. In computer programming, a data structure may be selected or designed to store data for the purpose of working on it with various algorithms. (1) 

Digital:  Digital describes electronic technology that generates, stores, and processes data in terms of two states: positive and non-positive. Positive is expressed or represented by the number 1 and non-positive by the number 0. Thus, data transmitted or stored with digital technology is expressed as a string of 0's and 1's. Each of these state digits is referred to as a bit (and a string of bits that a computer can address individually as a group is a byte).

Prior to digital technology, electronic transmission was limited to analog technology, which conveys data as electronic signals of varying frequency or amplitude that are added to carrier waves of a given frequency. Broadcast and phone transmission has conventionally used analog technology.

Digital technology is primarily used with new physical communications media, such as satellite and fiber optic transmission. A modem is used to convert the digital information in your computer to analog signals for your phone line and to convert analog phone signals to digital information for your computer. (1)

Encryption:  Encryption is the conversion of data into a form, called a ciphertext, that cannot be easily understood by unauthorized people. Decryption is the process of converting encrypted data back into its original form, so it can be understood.

Simple ciphers include the substitution of letters for numbers, the rotation of letters in the alphabet, and the "scrambling" of voice signals by inverting the sideband frequencies. More complex ciphers work according to sophisticated computer algorithms that rearrange the data bits in digital signals.

Encryption/decryption is especially important in wireless communications. This is because wireless circuits are easier to "tap" than their hard-wired counterparts. Nevertheless, encryption/decryption is a good idea when carrying out any kind of sensitive transaction, such as a credit-card purchase online, or the discussion of a company secret between different departments in the organization. The stronger the cipher -- that is, the harder it is for unauthorized people to break it -- the better, in general. However, as the strength of encryption/decryption increases, so does the cost. (1)

File Format:  In a computer, a file format is the layout of a file in terms of how the data within the file is organized. A program that uses the data in a file must be able to recognize and possibly access data within the file. For example, the program that we call a Web browser is able to process and display a file in the HTML file format so that it appears as a Web page, but it cannot display a file in a format designed for Microsoft's Excel program. A particular file format is often indicated as part of a file's name by a file name extension (suffix). Conventionally, the extension is separated by a period from the name and contains three or four letters that identify the format. A program that uses or recognizes a particular file format may or may not care whether the file has the appropriate extension name since it can actually examine the bits in the file to see whether the format (layout) is one it recognizes.  There are as many different file formats as there are different programs to process the files. A few of the more common file formats are:

• Word documents (.doc)
• Web text pages (.htm or .html)
• Web page images (.gif and .jpg)
• Adobe Postcript files (.ps)
• Adobe Acrobat files (.pdf)
• Executable programs (.exe)
• Multimedia files (.mp3 and others) (1)

File Sharing:  File sharing is the public or private sharing of computer data or space in a network with various levels of access privilege. While files can easily be shared outside a network (for example, simply by handing or mailing someone your file on a diskette), the term file sharing almost always means sharing files in a network, even if in a small local area network. File sharing allows a number of people to use the same file or file by some combination of being able to read or view it, write to or modify it, copy it, or print it. Typically, a file sharing system has one or more administrators. Users may all have the same or may have different levels of access privilege. File sharing can also mean having an allocated amount of personal file storage in a common file system. (1) 

File Server:  A storage system that provides data files to all connected users of a local network. Typically the file server is a computer with large disk storage which is able to record or send files as requested by the other connected (client) computers--the file server often appearing as another disk on their systems.  The data files are typically around a few kilobytes in size and are expected to be delivered within moments of request.  (4)

Hard Disk/Hard Drive:  A hard disk is part of a unit, often called a "disk drive," "hard drive," or "hard disk drive," that stores and provides relatively quick access to large amounts of data on an electromagnetically charged surface or set of surfaces. Today's computers typically come with a hard disk that contains several billion bytes (gigabytes) of storage.

A hard disk is really a set of stacked "disks," each of which, like phonograph records, has data recorded electromagnetically in concentric circles or "tracks" on the disk. A "head" (something like a phonograph arm but in a relatively fixed position) records (writes) or reads the information on the tracks. Two heads, one on each side of a disk, read or write the data as the disk spins. Each read or write operation requires that data be located, which is an operation called a "seek." (Data already in a disk cache, however, will be located more quickly.)  (1)

Standard Units:

Connectivity and Networking Terminology 

Broadband:  High-speed transmission. The term is commonly used to refer to communications lines or services at T1 rates (1.544 Mbps) and above. The speed threshold of broadband is subjective and can be above or below T1. Some claim 45 Mbps is the starting point of broadband. In every case however, it implies transmitting at higher speeds than what was common before. Broadband often refers to Internet access using cable modems and DSL, both of which deliver speeds above and below T1. See T1, cable modem and DSL. (2) 

Cable Modem:  A cable modem is a device that enables you to hook up your PC to a local cable TV line and receive data at about 1.5 Mbps. This data rate far exceeds that of the prevalent 28.8 and 56 Kbps telephone modems and the up to 128 Kbps of Integrated Services Digital Network (ISDN) and is about the data rate available to subscribers of Digital Subscriber Line (DSL) telephone service. A cable modem can be added to or integrated with a set-top box that provides your TV set with channels for Internet access. In most cases, cable modems are furnished as part of the cable access service and are not purchased directly and installed by the subscriber.

A cable modem has two connections: one to the cable wall outlet and the other to a PC or to a set-top box for a TV set. Although a cable modem does modulation between analog and digital signals, it is a much more complex device than a telephone modem. It can be an external device or it can be integrated within a computer or set-top box. Typically, the cable modem attaches to a standard 10BASE-T Ethernet card in the computer.

The actual bandwidth for Internet service over a cable TV line is up to 27 Mbps on the download path to the subscriber with about 2.5 Mbps of bandwidth for interactive responses in the other direction. However, since the local provider may not be connected to the Internet on a line faster than a T-carrier system at 1.5 Mpbs, a more likely data rate will be close to 1.5 Mpbs.

In addition to the faster data rate, an advantage of cable over telephone Internet access is that it is a continuous connection.  (1) 

Dark Fiber:  Dark fiber is optical fiber infrastructure (cabling and repeaters) that is currently in place but is not being used. Optical fiber conveys information in the form of light pulses so the "dark" means no light pulses are being sent. For example, some electric utilities have installed optical fiber cable where they already have power lines installed in the expectation that they can lease the infrastructure to telephone or cable TV companies or use it to interconnect their own offices. To the extent that these installations are unused, they are described as dark.  

"Dark fiber service" is service provided by local exchange carriers (LECs) for the maintenance of optical fiber transmission capacity between customer locations in which the light for the fiber is provided by the customer rather than the LEC.  (1) 

Dial-Up:  Dial-up pertains to a telephone connection in a system of many lines shared by many users. A dial-up connection is established and maintained for a limited time duration. The alternative is a dedicated connection, which is continuously in place. Dial-up lines are sometimes called switched lines and dedicated lines are called nonswitched lines. A dedicated line is often a leased line that is rented from a telephone company.   A dial-up connection can be initiated manually or automatically by your computer's modem or other device. (1) 

DSL:  DSL (Digital Subscriber Line) is a technology for bringing high-bandwidth information to homes and small businesses over ordinary copper telephone lines. xDSL refers to different variations of DSL, such as ADSL, HDSL, and RADSL. Assuming your home or small business is close enough to a telephone company central office that offers DSL service, you may be able to receive data at rates up to 6.1 megabits (millions of bits) per second (of a theoretical 8.448 megabits per second), enabling continuous transmission of motion video, audio, and even 3-D effects. More typically, individual connections will provide from 1.544 Mbps to 512 Kbps downstream and about 128 Kbps upstream. A DSL line can carry both data and voice signals and the data part of the line is continuously connected. DSL installations began in 1998 and will continue at a greatly increased pace through the next decade in a number of communities in the U.S. and elsewhere. Compaq, Intel, and Microsoft working with telephone companies have developed a standard and easier-to-install form of ADSL called G.lite that is accelerating deployment. DSL is expected to replace ISDN in many areas and to compete with the cable modem in bringing multimedia and 3-D to homes and small businesses. (1) 

Ethernet:   A type of high-speed network for interconnecting computing devices. Ethernet can be either 10 or 100 Mbps (Fast Ethernet). Ethernet is a trademark of Xerox Corporation, Inc. (4) 

ISDN:  ISDN (Integrated Services Digital Network) is a set of CCITT/ITU standards for digital transmission over ordinary telephone copper wire as well as over other media. Home and business users who install an ISDN adapter (in place of a modem) can see highly-graphic Web pages arriving very quickly (up to 128 Kbps). ISDN requires adapters at both ends of the transmission so your access provider also needs an ISDN adapter. ISDN is generally available from your phone company in most urban areas in the United States and Europe. (1) 

LAN:  A local area network (LAN) is a group of computers and associated devices that share a common communications line and typically share the resources of a single processor or server within a small geographic area (for example, within an office building). Usually, the server has applications and data storage that are shared in common by multiple computer users. A local area network may serve as few as two or three users (for example, in a home network) or many as thousands of users (for example, in an FDDI network).

Typically, a suite of application programs can be kept on the LAN server. Users who need an application frequently can download it once and then run it from their local hard disk. Users can order printing and other services as needed through applications run on the LAN server. A user can share files with others at the LAN server; read and write access is maintained by a LAN administrator.

A LAN server may also be used as a Web server if safeguards are taken to secure internal applications and data from outside access.  (1)

Last-Mile Technology:  Last-mile technology is any telecommunications technology, such as wireless radio, that carries signals from the broad telecommunication along the relatively short distance (hence, the "last mile") to and from the home or business. Or to put it another way: the infrastructure at the neighborhood level. In many communities, last-mile technology represents a major remaining challenge to high-bandwidth applications such as on-demand television, fast Internet access, and Web pages full of multimedia effects.

Today, in addition to "plain old telephone (dial-up) service", last-mile technologies to deliver voice, data, and TV can include:

• ISDN, a somewhat faster technology than regular phone service
• Digital Subscriber Line (DSL) over existing telephone twisted pair lines
• Cable and the cable modem for data, using the same installed coaxial cable that already is used for television
• wireless, including services such as DirecTV
• Less frequently because of the installation expense, optical fiber and its transmission technologies  (1)

Modem:  A modem modulates outgoing digital signals from a computer or other digital device to analog signals for a conventional copper twisted pair telephone line and demodulates the incoming analog signal and converts it to a digital signal for the digital device.

In recent years, the 2400 bits per second modem that could carry e-mail has become obsolete. 14.4 Kbps and 28.8 Kbps modems were temporary landing places on the way to the much higher bandwidth devices and carriers of tomorrow. From early 1998, most new personal computers came with 56 Kbps modems. By comparison, using a digital Integrated Services Digital Network adapter instead of a conventional modem, the same telephone wire can now carry up to 128 Kbps. With Digital Subscriber Line (DSL) systems, now being deployed in a number of communities, bandwidth on twisted-pair can be in the megabit range.  (1)

T-1, T-3:  The T-carrier system, introduced by the Bell System in the U.S. in the 1960s, was the first successful system that supported digitized voice transmission. The original transmission rate (1.544 Mbps) in the T-1 line is in common use today in Internet service provider (ISP) connections to the Internet. Another level, the T-3 line, providing 44.736 Mbps, is also commonly used by Internet service providers. Another commonly installed service is a fractional T-1, which is the rental of some portion of the 24 channels in a T-1 line, with the other channels going unused. (1) 

WAN:  A wide area network (WAN) is a geographically dispersed telecommunications network. The term distinguishes a broader telecommunication structure from a  local area network (LAN). A wide area network may be privately owned or rented, but the term usually connotes the inclusion of public (shared user) networks. An intermediate form of network in terms of geography is a metropolitan area network (MAN). (1) 

Wireless:  Wireless is a term used to describe telecommunications in which electromagnetic waves (rather than some form of wire) carry the signal over part or all of the communication path. Some monitoring devices, such as intrusion alarms, employ acoustic waves at frequencies above the range of human hearing; these are also sometimes classified as wireless.

The first wireless transmitters went on the air in the early 20th century using radiotelegraphy (Morse code). Later, as modulation made it possible to transmit voices and music via wireless, the medium came to be called "radio." With the advent of television, fax, data communication, and the effective use of a larger portion of the spectrum, the term "wireless" has been resurrected. (1) 

Wireless LAN:  A wireless LAN is one in which a mobile user can connect to a local area network (LAN) through a wireless (radio) connection. The standard protocol includes an encryption method, the Wired Equivalent Privacy algorithm.

High-bandwidth allocation for wireless will make possible a relatively low-cost wiring of classrooms in the United States. A similar frequency allocation has been made in Europe. Hospitals and businesses are also expected to install wireless LAN systems where existing LANs are not already in place.  (1)

Internet Terminology

Active Server Page (ASP):  An Active Server Page (ASP) is an HTML Web page that includes one or more scripts (small embedded programs) that are processed on a Microsoft Web server before the page is sent to the user. An ASP is somewhat similar to a server-side include or a common gateway interface (CGI) application in that all involve programs that run on the server, usually tailoring a page for the user. Typically, the script in the Web page at the server uses input received as the result of the user's request for the page to access data from a database and then builds or customizes the page on the fly before sending it to the requestor. (1) 

Application Server:  An application server is a server program in a computer in a distributed network that provides the business logic for an application program. The application server is frequently viewed as part of a three-tier application, consisting of a graphical user interface (GUI) server, an application (business logic) server, and a database and transaction server. More descriptively, it can be viewed as dividing an application into:

1.      A first-tier, front-end, Web browser-based graphical user interface, usually at a personal computer or workstation

2.      A middle-tier business logic application or set of applications, possibly on a local area network or intranet server

3.      A third-tier, back-end, database and transaction server, sometimes on a mainframe or large server.  (1)

Browser:  A browser is an application program that provides a way to look at and interact with all the information on the World Wide Web. The word "browser" seems to have originated prior to the Web as a generic term for user interfaces that let you browse (navigate through and read) text files online. By the time the first Web browser with a graphical user interface was generally available (Mosaic, in 1993), the term seemed to apply to Web content, too. Technically, a Web browser is a client program that uses the Hypertext Transfer Protocol (HTTP) to make requests of Web servers throughout the Internet on behalf of the browser user. A commercial version of the original browser, Mosaic, is in use. Many of the user interface features in Mosaic, however, went into the first widely-used browser, Netscape Navigator. Microsoft followed with its Microsoft Internet Explorer. Today, these two browsers are the only two browsers that the vast majority of Internet users are aware of. Although the online services, such as America Online, originally had their own browsers, virtually all now offer the Netscape or Microsoft browser. Lynx is a text-only browser for UNIX shell and VMS users. Another recently offered and well-regarded browser is Opera.

While some browsers also support e-mail (indirectly through e-mail Web sites) and the File Transfer Protocol (FTP), a Web browser is not required for those Internet protocols and more specialized client programs are more popular.

Cache:  A cache (pronounced CASH) is a place to store something temporarily. The files you automatically request by looking at a Web page are stored on your hard disk in a cache subdirectory under the directory for your browser (for example, Internet Explorer). When you return to a page you've recently looked at, the browser can get it from the cache rather than the original server, saving you time and the network the burden of some additional traffic. You can usually vary the size of your cache, depending on your particular browser.

Computers include caches at several levels of operation, including cache memory and a disk cache. Caching can also be implemented for Internet content by distributing it to multiple servers that are periodically refreshed. (The use of the term in this context is closely related to the general concept of a distributed information base.)  (1)

Cache Server:  A cache server (sometimes called a cache engine) is a server relatively close to Internet users and typically within a business enterprise that saves (caches) Web pages and possibly FTP and other files that all server users have requested so that successive requests for these pages or files can be satisfied by the cache server rather than requiring the user of the Internet. A cache server not only serves its users by getting information more quickly but also reduces Internet traffic.

A cache server is almost always also a proxy server, which is a server that "represents" users by intercepting their Internet requests and managing them for users. Typically, this is because enterprise resources are being protected by a firewall server that allows outgoing requests to go out but needs to screen all incoming traffic. A proxy server helps match incoming messages with outgoing requests and is in a position to also cache the files that are received for later recall by any user. To the user, the proxy and cache servers are invisible; all Internet requests and returned responses appear to be coming from the addressed place on the Internet. (The proxy is not quite invisible; its IP address has to be specified as a configuration option to the browser or other protocol program.)  (1)

CGI:  The common gateway interface (CGI) is a standard way for a Web server to pass a Web user's request to an application program and to receive data back to forward to the user. When the user requests a Web page (for example, by clicking on a highlighted word or entering a Web site address), the server sends back the requested page. However, when a user fills out a form on a Web page and sends it in, it usually needs to be processed by an application program. The Web server typically passes the form information to a small application program that processes the data and may send back a confirmation message. This method or convention for passing data back and forth between the server and the application is called the common gateway interface (CGI). It is part of the Web's Hypertext Transfer Protocol (HTTP).

If you are creating a Web site and want a CGI application to get control, you specify the name of the application in the uniform resource locator (URL) that you code in an HTML file. This URL can be specified as part of the FORMS tags if you are creating a form.  (1)

Content Management System:   A content management system (CMS) is a system used to manage the content of a Web site. Typically, a CMS consists of two elements: the content management application (CMA) and the content delivery application (CDA). The CMA element allows the content manager or author, who may not know Hypertext Markup Language (HTML), to manage the creation, modification, and removal of content from a Web site without needing the expertise of a Webmaster. The CDA element uses and compiles that information to update the Web site. The features of a CMS system vary, but most include Web-based publishing, format management, revision control, and indexing, search, and retrieval.

The Web-based publishing feature allows individuals to use a template or a set of templates approved by the organization, as well as wizards and other tools to create or modify Web content. The format management feature allows documents including legacy electronic documents and scanned paper documents to be formatted into HTML or Portable Document Format (PDF) for the Web site. The revision control feature allows content to be updated to a newer version or restored to a previous version. Revision control also tracks any changes made to files by individuals. An additional feature is indexing, search, and retrieval. A CMS system indexes all data within an organization. Individuals can then search for data using keywords, which the CMS system retrieves.

Two factors must be considered before an organization decides to invest in a CMS. First, an organization's size and geographic dispersion must be considered especially if an organization is spread out over several countries. For these organizations, the transition to CMS is more difficult. Secondly, the diversity of the electronic data forms used within an organization must be considered. If an organization uses text documents, graphics, video, audio, and diagrams to convey information, the content will be more difficult to manage.  (1)

Cookie:  A cookie is information  that a Web site puts on your hard disk so that it can remember something about you at a later time. (More technically, it is information for future use that is stored by the server on the client side of a  client/server communication.) Typically, a cookie records your preferences when using a particular site. Using the Web's Hypertext Transfer Protocol (HTTP), each request for a Web page is independent of all other requests. For this reason, the Web page server has no memory of what pages it has sent to a user previously or anything about your previous visits. A cookie is a mechanism that allows the server to store its own information about a user on the user's own computer. You can view the cookies that have been stored on your hard disk (although the content stored in each cookie may not make much sense to you). The location of the cookies depends on the browser. Internet Explorer stores each cookie as a separate file under a Windows subdirectory. Netscape stores all cookies in a single cookies.txt fle. Opera stores them in a single cookies.dat file.   (1)

Customer Relationship Management (CRM):  CRM (customer relationship management) is an information industry term for methodologies, software, and usually Internet capabilities that help an enterprise manage customer relationships in an organized way. For example, an enterprise might build a database about its customers that described relationships in sufficient detail so that management, salespeople, people providing service, and perhaps the customer directly could access information, match customer needs with product plans and offerings, remind customers of service requirements, know what other products a customer had purchased, and so forth. (1) 

Domain:  A domain name locates an organization or other entity on the Internet. For example, the domain name

www.totalbaseball.com locates an Internet address for "totalbaseball.com" at Internet point 199.0.0.2 and a particular host server named "www". The "com" part of the domain name reflects the purpose of the organization or entity (in this example, "commercial") and is called the top-level domain name. The "totalbaseball" part of the domain name defines the organization or entity and together with the top-level is called the second-level domain name. The second-level domain name maps to and can be thought of as the "readable" version of the Internet address. (1) 

DHTML:  Dynamic HTML is a collective term for a combination of new Hypertext Markup Language (HTML) tags and options, that will let you create Web pages more animated and more responsive to user interaction than previous versions of HTML. Much of dynamic HTML is specified in HTML 4.0. Simple examples of dynamic HTML pages would include (1) having the color of a text heading change when a user passes a mouse over it or (2) allowing a user to "drag and drop" an image to another place on a Web page. Dynamic HTML can allow Web documents to look and act like desktop applications or multimedia productions. (1)

Data Aggregation:  Data aggregation is any process in which information is gathered and expressed in a summary form, for purposes such as statistical analysis. For example, the Web site of a music club might collect aggregate data about music searches, and analyze the resultant data to inform the music club owners about the most frequently requested artists and CDs. A common aggregation purpose is to get more information about particular groups, based on any specific variables, such as age, profession, or income. The information about such groups can then be used for Web site personalization, to choose content and advertising likely to appeal to an individual belonging to one or more groups for which data has been collected. For example, a music club might advertise certain music based on the age of the user and the data aggregate for their age group.  (1) 

Digital Library:   A digital library is a collection of documents in organized electronic form, available on the Internet or on CD-ROM (compact-disk read-only memory) disks. Depending on the specific library, a user may be able to access magazine articles, books, papers, images, sound files, and videos.  On the Internet, the use of a digital library is enhanced by a broadband connection such as cable modem or DSL. Dial-up connections can be used to access plain-text documents and some documents containing images, but for complex files and those with animated video content, a downstream data speed of at least several hundred kilobits per second (Kbps) can make the user's experience less tedious, as well as more informative. Internet-based digital libraries can be updated on a daily basis. This is one of the greatest assets of this emerging technology.

On CD-ROM, the amount of data is limited to several hundred megabytes (MB) per disk, but access is generally much faster than on an Internet connection. Several CD-ROMs can be combined in a set, and because the disks are small, a large library can be accommodated in a reasonable physical space. The main limitation of CD-ROM is the fact that updating cannot be done as frequently as on the Internet. In addition, producing and distributing CD-ROMs involves overhead costs that are largely nonexistent in Internet-based libraries.

Electronic distribution of intellectual and artistic property has authors, agents, and publishers concerned about the possibility of copyright infringement. It is much easier to copy a CD-ROM, or to download an electronic book and make unauthorized copies of it, than it is to reproduce bound volumes and distribute them illegitimately. Fundamental changes in copyright law - and/or changes in the way in which the laws are enforced - are likely to occur as digital libraries expand and their use becomes more widespread.  (1) 

Discussion Board:  A discussion board is a general term for any online "bulletin board" where you can leave and expect to see responses to messages you have left. Or you can just read the board. Bulletin board services were invented for this purpose (as well as to allow for the exchange of uploaded/downloaded files). On the Internet, Usenet provides thousands of discussion boards. Discussion board software is now available that allows discussion boards to be added to a Web site. (1) 

Dublin Core:  Dublin Core is an initiative to create a digital "library card catalog" for the Web. Dublin Core is made up of 15 metadata (data that describes data) elements that offer expanded cataloging information and improved document indexing for search engine programs.

The 15 metadata elements used by Dublin Core are: title (the name given the resource), creator (the person or organization responsible for the content), subject (the topic covered), description (a textual outline of the content), publisher (those responsible for making the resource available), contributor (those who added to the content), date (when the resource was made available), type (a category for the content), format (how the resource is presented), identifier (numerical identifier for the content such as a URL), source (where the content originally derived from), language (in what language the content is written), relation (how the content relates to other resources, for instance, if it is a chapter in a book), coverage (where the resource is physically located), and rights (a link to a copyright notice).

The Dublin Core Metadata Initiative began in 1995, taking its name from the location of the original workshop, Dublin, Ohio. It has since become international in scope and has representatives from more than 20 countries now contributing. Dublin Core has always held that resource discovery should be independent from the medium of the resource. So, while Dublin Core targets electronic resources, it aims to be flexible enough to help in searches for more traditional formats of data too. Web sites, though, are the most common users of Dublin Core.  (1)

Enterprise Server:  An enterprise server is a computer containing programs that collectively serve the needs of an enterprise rather than a single user, department, or specialized application. Historically, mainframe-sized computers have been enterprise servers although they were not referred to as servers until recently. As smaller, usually UNIX-based servers and Wintel computers have become faster and have been provided with enterprise-wide program management capabilities, they also been referred to as enterprise servers.   Some companies use enterprise server to describe a "superprogram" that runs under the operating system in a computer and provides services for the system administrator and for the business application programs and more specialized servers that run in the computer. Before this usage originated, such services were sometimes considered part of the operating system itself or came in separate software packages. Originally, many services provided by an enterprise server tended to be available only on IBM or similar mainframe computers while less powerful computers ran specialized applications. As these smaller "server" computers (such as those from Sun Microsystems and H-P) became better adapted for business (and recently Internet) applications, the bundle of services required to manage a company-wide set of applications was renamed "the enterprise server." More specialized servers include the Web server, firewall server, database server, and so forth.  (1)

File Transfer Protocol (FTP):  A standard Internet protocol, FTP is the simplest way to exchange files between computers on the Internet. Like the Hypertext Transfer Protocol (HTTP), which transfers displayable Web pages and related files, and the Simple Mail Transfer Protocol (SMTP), which transfers e-mail, FTP is an application protocol that uses the Internet's standard (TCP/IP) protocols. FTP is commonly used to transfer Web page files from their creator to the computer that acts as their server for everyone on the Internet. It's also commonly used to download programs and other files to your computer from other servers. Your Web browser can make FTP requests to download programs you select from a Web page. Using FTP, you can also update (delete, rename, move, and copy) files at a server. You need to logon to an FTP server.  (1) 

Firewall:  A firewall is a set of related programs, located at a network gateway server, that protects the resources of a private network from users from other networks. (The term also implies the security policy that is used with the programs.) An enterprise with an intranet that allows its workers access to the wider Internet installs a firewall to prevent outsiders from accessing its own private data resources and for controlling what outside resources its own users have access to.

Basically, a firewall, working closely with a router program, examines each network packet to determine whether to forward it toward its destination. A firewall also includes or works with a proxy server that makes network requests on behalf of workstation users. A firewall is often installed in a specially designated computer separate from the rest of the network so that no incoming request can get directly at private network resources.

There are a number of firewall screening methods. A simple one is to screen requests to make sure they come from acceptable (previously identified) domain name and Internet Protocol addresses. For mobile users, firewalls allow remote access in to the private network by the use of secure logon procedures and authentication certificates. (1)

Hit:  A hit is a single file request in the access log of a Web server.  A request for an HTML page with three graphic images will result in four hits in the log: one for the HTML text file and one for each of the graphic image files. While a hit is a meaningful measure of how much traffic a server handles, it can be a misleading indicator of how many pages are being looked at.  Page views and IP visits are a more reliable method of tracking site traffic. (1) 

HTML:  HTML (Hypertext Markup Language) is the set of symbols or codes inserted in a file intended for display on a World Wide Web browser page. The markup tells the Web browser how to display a Web page's words and images for the user. Each individual markup symbol is referred to as an element or tag. Some elements come in pairs that indicate when some display effect is to begin and when it is to end.

HTML is generally adhered to by the major browsers, Microsoft's Internet Explorer and Netscape's Navigator, which also provide some additional non-standard codes. The current version of HTML is HTML 4.0. However, both Internet Explorer and Netscape implement some features differently and provide non-standard extensions. Web developers using the more advanced features of HTML 4 may have to design pages for both browsers and send out the appropriate version to a user. Significant features in HTML 4 are sometimes described in general as dynamic HTML. (1)

Hypertext:  Hypertext is the organization of information units into connected associations that a user can choose to make. An instance of such an association is called a link or hypertext link. (And the highlighted word "link" in the previous sentence is an example of a hypertext link.)

Hypertext was the main concept that led to the invention of the World Wide Web, which is, after all, nothing more (or less) than an enormous amount of information content connected by an enormous number of hypertext links. (1)

IP Address/IP Visits:  The Internet Protocol (IP) is the method or protocol by which data is sent from one computer to another on the Internet. Each computer (known as a host) on the Internet has at least one IP address that uniquely identifies it from all other computers on the Internet. When you send or receive data (for example, an e-mail note or a Web page), the message gets divided into little chunks called packets. Each of these packets contains both the sender's Internet address and the receiver's address. Any packet is sent first to a gateway computer that understands a small part of the Internet. The gateway computer reads the destination address and forwards the packet to an adjacent gateway that in turn reads the destination address and so forth across the Internet until one gateway recognizes the packet as belonging to a computer within its immediate neighborhood or domain. That gateway then forwards the packet directly to the computer whose address is specified.  Web site traffic may be measured in “IP Visits,” which corresponds to a computer’s unique IP address.  This measure is roughly comparable to the # of visitors a site receives, although it’s not exact. (1) 

Internet:  The Internet, sometimes called simply "the Net," is a worldwide system of computer networks - a network of networks in which users at any one computer can, if they have permission, get information from any other computer (and sometimes talk directly to users at other computers). It was conceived by the Advanced Research Projects Agency (ARPA) of the U.S. government in 1969 and was first known as the ARPANET. The original aim was to create a network that would allow users of a research computer at one university to be able to "talk to" research computers at other universities. A side benefit of ARPANet's design was that, because messages could be routed or rerouted in more than one direction, the network could continue to function even if parts of it were destroyed in the event of a military attack or other disaster.

Today, the Internet is a public, cooperative, and self-sustaining facility accessible to hundreds of millions of people worldwide. Physically, the Internet uses a portion of the total resources of the currently existing public telecommunication networks. Technically, what distinguishes the Internet is its use of a set of protocols called TCP/IP (for Transmission Control Protocol/Internet Protocol). Two recent adaptations of Internet technology, the intranet and the extranet, also make use of the TCP/IP protocol. (1)

ISP:  An ISP (Internet service provider) is a company that provides individuals and other companies access to the Internet and other related services such as Web site building and virtual hosting. An ISP has the equipment and the telecommunication line access required to have a point-of-presence on the Internet for the geographic area served. The larger ISPs have their own high-speed leased lines so that they are less dependent on the telecommunication providers and can provide better service to their customers. Among the largest national and regional ISPs are AT&T WorldNet, IBM Global Network, MCI, Netcom, UUNet, and PSINet. (1)

Java:  A general purpose programming language developed by Sun Microsystems and best known for its widespread use on the World Wide Web. Unlike other software, programs written in Java can run on any platform type (including set-top boxes), as long as they contain a Java Virtual Machine. Internet: java.sun.com. (4) 

JavaScript::  JavaScript is an interpreted programming or script language from Netscape. In general, script languages are easier and faster to code in than the more structured and compiled languages such as C and C++. Script languages generally take longer to process than compiled languages, but are very useful for shorter programs. 

JavaScript is used in Web site development to do such things as:

·         Automatically change a formatted date on a Web page

·         Cause a linked-to page to appear in a popup window

·         Cause text or a graphic image to change during a mouse rollover

JavaScript uses some of the same ideas found in Java, the compiled object-oriented programming derived from C++. JavaScript code can be imbedded in HTML pages and interpreted by the Web browser (or client). JavaScript can also be run at the server as in Microsoft's Active Server Pages before the page is sent to the requestor. Both Microsoft and Netscape browsers support JavaScript, but sometimes in slightly different ways. (1)

Listserv:  Listserv, like Majordomo, is a small program that automatically redistributes e-mail to names on a mailing list. Users can subscribe to a mailing list by sending an e-mail note to a mailing list they learn about; listserv will automatically add the name and distribute future e-mail postings to every subscriber. (Requests to subscribe and unsubscribe are sent to a special address so that all subscribers do not see these requests.) These programs are also known as list servers. (1) 

Log File:  An access log is a list of all the requests for individual files that people have requested from a Web site. These files will include the HTML files and their imbedded graphic images and any other associated files that get transmitted. The access log (sometimes referred to as the "raw data") can be analyzed and summarized by another program.

In general, an access log can be analyzed to tell you:

·         The number of visitors (unique first-time requests) to a home page

·         The origin of the visitors in terms of their associated server's domain name (for example, visitors from .edu, .com, and .gov sites and from the online services)

·         How many requests for each page at the site, which can be presented with the pages with most requests listed first

·         Usage patterns in terms of time of day, day of week, and seasonally  (1)

Metadata:  Meta is a prefix that in most information technology usages means "an underlying definition or description." Thus, metadata is a definition or description of data—data about data.   Metadata describes how and when and by whom a particular set of data was collected, and how the data is formatted. Metadata is essential for understanding information stored in data warehouses.  The term may refer to detailed compilations such as data dictonaries and repositories that provide a fair amount of information about each data element. It may also refer to any descriptive item about data, such as the content of an HTML meta tag or a title field in a media file. Examples of standard metadata protocols include the Dublin Core.  (2, 3)

Metatag:  A meta tag is a tag (that is, a coding statement) in the Hypertext Markup Language (HTML) that describes some aspect of the contents of a Web page. The information that you provide in a meta tag is used by search engines to index a page so that someone searching for the kind of information the page contains will be able to find it. The meta tag is placed near the top of the HTML in a Web page as part of the heading.

There are several kinds of meta tags, but the most important for search engine indexing are the keywords meta tag and the description meta tag. The keywords meta tag lists the words or phrases that best describe the contents of the page. The description meta tag includes a brief one- or two-sentence description of the page. Both the keywords and the description are used by search engines in adding a page to their index. Some search engines also use the description to show the searcher a summary of the page's contents.

Although most search engines also use the contents of a page as a way to determine how to index it, the creator of a Web page should be sure to include meta tags with appropriate keywords and description. Well-written meta tags can help make the page rank higher in search results.  (1) 

MPEG:  MPEG, the Moving Picture Experts Group, develops standards for digital video and digital audio compression. It operates under the auspices of the International Organization for Standardization (ISO). The MPEG standards are an evolving series, each designed for a different purpose.

To use MPEG video files, you need a personal computer with sufficient processor speed, internal memory, and hard disk space to handle and play the typically large MPEG file (which has a file name suffix of .mpg). You also need an MPEG viewer or client software that plays MPEG files. (Note that .mp3 file suffixes indicate MP3 (MPEG-1 audio layer-3) files, not MPEG-3 standard files.) You can download shareware or commercial MPEG players from a number of sites on the Web.  (1)

Multimedia:  Multimedia is more than one concurrent presentation medium (for example, on CD-ROM or a Web site). Although still images are a different medium than text, multimedia is typically used to mean the combination of text, sound, and/or motion video. Some people might say that the addition of animated images (for example, animated GIF on the Web) produces multimedia, but it has typically meant one of the following:

·         Text and sound

·         Text, sound, and still or animated graphic images

·         Text, sound, and video images

·         Video and sound

·         Multiple display areas, images, or presentations presented concurrently

·         In live situations, the use of a speaker or actors and "props" together with sound, images, and motion video

Multimedia can arguably be distinguished from traditional motion pictures or movies both by the scale of the production (multimedia is usually smaller and less expensive) and by the possibility of audience interactivity or involvement (in which case, it is usually called interactive multimedia). Interactive elements can include: voice command, mouse manipulation, text entry, touch screen, video capture of the user, or live participation (in live presentations).  (1) 

Page View:  A Web page, which can be of any length and can contain any number of graphic images. The HTML page itself and every image are each considered a hit. Thus, one page view equals one hit only if there are no graphics on the page. (1) 

PDF:  PDF (Portable Document Format) is a file format that has captured all the elements of a printed document as an electronic image that you can view, navigate, print, or forward to someone else. PDF files are created using Adobe Acrobat, Acrobat Capture, or similar products. To view and use the files, you need the free Acrobat Reader, which you can easily download. Once you've downloaded the Reader, it will start automatically whenever you want to look at a PDF file.  

PDF files are especially useful for documents such as magazine articles, product brochures, or flyers in which you want to preserve the original graphic appearance online. A PDF file contains one or more page images, each of which you can zoom in on or out from. You can page forward and backward.  (1) 

Personalization:  On a Web site, personalization is the process of tailoring pages to individual users' characteristics or preferences.  Personalization is a means of meeting the customer's needs more effectively and efficiently, making interactions faster and easier and, consequently, increasing customer satisfaction and the likelihood of repeat visits.  If you've ever bought a book from Amazon, for example, the next time you visit they will - like a friendly and helpful sales clerk - greet you by name and tell you about products in stock that they think you might like (such as more books by the same author, or books purchased by other people who also bought the book that you purchased). Many portal sites, such as Yahoo allow site visitors to customize the page with selected news categories, local weather reports, and other features.

In addition to use of the cookie, the technologies behind personalization include:

·         Collaborative filtering, in which a filter is applied to information from different sites to select relevant data that may apply to the specific e-commerce experience of a customer or specific group of customers

·         User profiling, using data collected from a number of different sites, which can result in the creation a personalized Web page before the user has been formally

·         Data analysis tools used to predict likely future interactions.  (1) 

Plug-In:  Plug-in applications are programs that can easily be installed and used as part of your Web browser. Initially, the Netscape browser allowed you to download, install, and define supplementary programs that played sound or motion video or performed other functions. These were called helper applications. However, these applications run as a separate application and require that a second window be opened. A plug-in application is recognized automatically by the browser and its function is integrated into the main HTML file that is being presented. (1) 

Proxy Server:  In an enterprise that uses the Internet, a proxy server is a server that acts as an intermediary between a workstation user and the Internet so that the enterprise can ensure security, administrative control, and caching service. A proxy server is associated with or part of a gateway server that separates the enterprise network from the outside network and a firewall server that protects the enterprise network from outside intrusion.

A proxy server receives a request for an Internet service (such as a Web page request) from a user. If it passes filtering requirements, the proxy server, assuming it is also a cache server, looks in its local cache of previously downloaded Web pages. If it finds the page, it returns it to the user without needing to forward the request to the Internet. If the page is not in the cache, the proxy server, acting as a client on behalf of the user, uses one of its own IP addresses to request the page from the server out on the Internet. When the page is returned, the proxy server relates it to the original request and forwards it on to the user.

To the user, the proxy server is invisible; all Internet requests and returned responses appear to be directly with the addressed Internet server. (The proxy is not quite invisible; its IP address has to be specified as a configuration option to the browser or other protocol program.)

An advantage of a proxy server is that its cache can serve all users. If one or more Internet sites are frequently requested, these are likely to be in the proxy's cache, which will improve user response time. In fact, there are special servers called cache servers. A proxy can also do logging.

The functions of proxy, firewall, and caching can be in separate server programs or combined in a single package. Different server programs can be in different computers. For example, a proxy server may in the same machine with a firewall server or it may be on a separate server and forward requests through the firewall. (1)

Search Engine:  On the Internet, a search engine is a coordinated set of programs that includes:

·         A spider (also called a "crawler" or a "bot") that goes to every page or representative pages on every Web site that wants to be searchable and reads it, using hypertext links on each page to discover and read a site's other pages

·         A program that creates a huge index (sometimes called a "catalog") from the pages that have been read

·         A program that receives your search request, compares it to the entries in the index, and returns results to you.

An alternative to using a search engine is to explore a structured directory of topics. Yahoo, which also lets you use its search engine, is the most widely-used directory on the Web. A number of Web portal sites offer both the search engine and directory approaches to finding information.  (1)

Server:  In general, a server is a computer program that provides services to other computer programs in the same or other computers.   The computer that a server program runs in is also frequently referred to as a server (though it may contain a number of server and client programs).  In the client/server programming model, a server is a program that awaits and fulfills requests from client programs in the same or other computers. A given application in a computer may function as a client with requests for services from other programs and also as a server of requests from other programs.

Specific to the Web, a Web server is the computer program (housed in a computer) that serves requested HTML pages or files. A Web client is the requesting program associated with the user. The Web browser in your computer is a client that requests HTML files from Web servers.  (1) 

Server Side Include:  A server-side include is a variable value (for example, a file "Last modified" date) that a server can include in an HTML file before it sends it to the requestor. If you're creating a Web page, you can insert an include statement in the HTML file that looks like this:

<!--#echo var="LAST_MODIFIED"-->

and the server will obtain the last-modified date for the file and insert it before the HTML file is sent to requestors.

LAST_MODIFIED is one of several environment variables that an operating system can keep track of and that can be accessible to a server program. The server administrator can make these environment variables usable when the system is set up.  (1)

Spam:  Spam is unsolicited e-mail on the Internet. From the sender's point-of-view, it's a form of bulk mail, often to a list culled from subscribers to a Usenet discussion group or obtained by companies that specialize in creating e-mail distribution lists. To the receiver, it usually seems like junk e-mail. In general, it's not considered good netiquette to send spam. It's generally equivalent to unsolicited phone marketing calls except that the user pays for part of the message since everyone shares the cost of maintaining the Internet.

Some apparently unsolicited e-mail is, in fact, e-mail people agreed to receive when they registered with a site and checked a box agreeing to receive postings about particular products or interests. This is known as both opt-in e-mail and permission-based e-mail. (1)

Streaming Media:  Streaming media is sound (audio) and pictures (video) that are transmitted on the Internet in a streaming or continuous fashion, using data packets. The most effective reception of streaming media requires some form of broadband technology such as cable modem or DSL. (1) 

Streaming Video:  Streaming video is a sequence of "moving images" that are sent in compressed form over the Internet and displayed by the viewer as they arrive. Streaming media is streaming video with sound. With streaming video or streaming media, a Web user does not have to wait to download a large file before seeing the video or hearing the sound. Instead, the media is sent in a continuous stream and is played as it arrives. The user needs a player, which is a special program that uncompresses and sends video data to the display and audio data to speakers. A player can be either an integral part of a browser or downloaded from the software maker's Web site.

Major streaming video and streaming media technologies include RealSystem G2 from RealNetwork, Microsoft Windows Media Technologies (including its NetShow Services and Theater Server), and VDO. Microsoft's approach uses the standard MPEG compression algorithm for video. The other approaches use proprietary algorithms. (The program that does the compression and decompression is sometimes called the codec.) Microsoft's technology offers streaming audio at up to 96 Kbps and streaming video at up to 8 Mbps (for the NetShow Theater Server). However, for most Web users, the streaming video will be limited to the data rates of the connection (for example, up to 128 Kbps with an ISDN connection). Microsoft's streaming media files are in its Advanced Streaming Format (ASF).

Streaming video is usually sent from prerecorded video files, but can be distributed as part of a live broadcast "feed." In a live broadcast, the video signal is converted into a compressed digital signal and transmitted from a special Web server that is able to do multicast, sending the same file to multiple users at the same time.  (1) 

Style Sheet:  A term extended from print publishing to online media, a style sheet is a definition of a document's appearance in terms of such elements as:

·         The default typeface, size, and color for headings and body text

·         How all or individual sections should be laid out in terms of space (for example, two newspaper columns, one column with headings having hanging heads, and so forth).

·         Any boilerplate content that is to be included on certain pages (for example, copyright statements)

Typically, a style sheet is specified at the beginning of an electronic document, either by embedding it or linking to it. This style sheet applies to the entire document. As necessary, specific elements of the overall style sheet can be overridden by special coding that applies to a given section of the document.   For Web pages, a style sheet performs a similar function. The style elements can be specified once for the entire document by either imbedding the style rules in the document heading or cross-referring (linking to or importing) a separate style sheet. A browser may allow the user to override some or all of the style sheet attributes.  (1)

Syndication:  In general, syndication is the supply of material for reuse and integration with other material, often through a paid service subscription. For many years mainly a feature of print media, today content syndication is the way a great deal of information is disseminated across the Web. Reuters, for xample, provides online news content to over 900 Web sites and portals, such as Yahoo and America Online.

Two crucial components for the further development of the industry built on online syndication have been cited as: the need for a standardized data exchange mechanism, and the need for a standardized metadata vocabulary (since suppliers and subscribers are often using different and incompatible technologies). An organization made up of content providers and vendors, the Publishing Requirements for Industry Standard Metadata (PRISM) working group is collaborating to develop a standard vocabulary.  (1)

URL:  A URL (Uniform Resource Locator) is the address of a file (resource) accessible on the Internet. The type of resource depends on the Internet application protocol. Using the World Wide Web's protocol, the Hypertext Transfer Protocol (HTTP) , the resource can be an HTML page, an image file, a program such as a common gateway interface application or Java applet, or any other file supported by HTTP. The URL contains the name of the protocol required to access the resource, a domain name that identifies a specific computer on the Internet, and a hierarchical description of a file location on the computer.  On the Web (which uses the Hypertext Transfer Protocol), an example of a URL is:  http://www.mhrcc.org/kingston (1) 

Usability:  Usability is the measure of a product's potential to accomplish the goals of the user. In information technology, the term is often used in relation to software applications and Web sites.  Some factors used in determining product usability are ease-of-use, visual consistency, and a clear, defined process for evolution.

Usability testing is a method by which users of a product are asked to perform certain tasks in an effort to measure the product's ease-of-use, task time, and the user's perception of the experience. Usability testing can be done formally, in a usability lab with video cameras, or informally, with paper mock-ups of an application or Web site. Changes are made to the application or site based on the findings of the usability tests. Whether the test is formal or informal, usability test participants are encouraged to think aloud and voice their every opinion. Usability testing is best used in conjunction with user-centered design, a method by which a product is designed according to the needs and specifications of users.  (1)

Video Server:  A storage system that provides audio and video storage for a network of clients. While there are some analog systems based on optical disks, most used in professional and broadcast applications are based on digital disk storage.

Aside from those used for video on demand (VOD), video servers are applied in three areas of television operation: transmission, post production and news. Compared to general purpose file servers, video severs must handle far more data, files are larger and must be continuously delivered.

There is no general specification for video servers and so the performance between models varies greatly according to storage capacity, number of channels, compression ratio and degree of access to store material--the latter having a profound influence.

Store sizes are very large, typically up to 500 Gigabytes or more. Operation depends entirely on connected devices, edit suites, automation systems, secondary servers, etc., so the effectiveness of the necessary remote control and video networking is vital to success. (4)

Walled Garden/Virtual Channel:  On the Internet, a walled garden is an environment that controls the user's access to Web content and services. In effect, the walled garden directs the user's navigation within particular areas, to allow access to a selection of material, or prevent access to other material. In 1999, for example, America Online (AOL) UK's Kid Channel established a walled garden to prevent access to inappropriate Web sites.

Because wireless devices such as smartphones are often limited to the content provided by their carriers, the portion of the Web that is available to wireless users is frequently referred to as a walled garden. Speaking of the Web as a whole, AOL is generally considered the major - and most successful - practitioner of the walled garden approach. According to a spokesperson from Disney (arguing against the recent AOL - Time Warner merger), 85% of AOL users never leave AOL territory; according to The Economist, almost 40% of the time Americans spend on the Web is within the confines of AOL's walled garden.

Virtual Channels provided by cable operators also utilize the walled garden approach.  A Web-like virtual channel may provide the basic functions of a Web site (similar navigation/interactivity) without allowing more advanced functions and navigation to the rest of the Internet.  In function, it performs like a Web site that has been pressed onto a CD-ROM, for use on a machine that has no Internet connection.  (1)

Webcast:  The term "Webcasting" is used to describe the ability to use the Web to deliver live or delayed versions of sound or video broadcasts. NetTalk Live! is an example of the former. They use an Internet site to deliver a RealAudio sound version of a live radio and television program at 11 pm (CST) each Sunday night. (They call this a triplecast.)  

CNet and some other Web sites use the term "Webcast" to describe delayed or preview versions of movies, music videos, or regular radio and television broadcasts as a way to promote the live broadcasts. Each sample is known as a Webisode. Viewing Webcasts requires having an appropriate video viewing application such as the NetShow, RealVideo, or VXtreme streaming video players; these can usually be downloaded from any site offering a Webcast. (1)

Web server:  A Web server is a program that, using the client/server model and the World Wide Web's Hypertext Transfer Protocol (HTTP), serves the files that form Web pages to Web users (whose computers contain HTTP clients that forward their requests). Every computer on the Internet that contains a Web site must have a Web server program. Two leading Web servers are Apache, the most widely-installed Web server, and Microsoft's Internet Information Server (IIS).

Web servers often come as part of a larger package of Internet- and intranet-related programs for serving e-mail, downloading requests for File Transfer Protocol (FTP) files, and building and publishing Web pages. Considerations in choosing a Web server include how well it works with the operating system and other servers, its ability to handle server-side programming, security characteristics, and publishing, search engine, and site building tools that may come with it.  (1)

Wireless Web:  The wireless Web refers to use of the World Wide Web through a wireless device, such as a cellular telephone or personal digital assistant (PDA). Wireless Web connection provides anytime/anywhere connection to e-mail, mobile banking, instant messaging, weather and travel information, and other services. In general, sites aiming to accommodate wireless users must provide services in a format displayable on typically small wireless devices. It is estimated that 95% of wireless Internet devices being manufactured today use the Wireless Application Protocol (WAP) developed by Ericsson, Motorola, Nokia, and Unwired Planet (now Phone.com) for presenting content. The wireless Web is not gaining in popularity as quickly as some have predicted. The low bandwidth of today's wireless service, relatively high usage charges, and small and difficult-to-use input and output devices contribute to impeding growth, a condition that has been referred to as "wapathy" (WAP apathy). (1)

World Wide Web:  A technical definition of the World Wide Web is: all the resources and users on the Internet that are using the Hypertext Transfer Protocol (HTTP).

XML:  XML (Extensible Markup Language) is a flexible way to create common information formats and share both the format and the data on the World Wide Web, intranets, and elsewhere.  XML is similar to the language of today's Web pages, the Hypertext Markup Language (HTML). Both XML and HTML contain markup symbols to describe the contents of a page or file. HTML, however, describes the content of a Web page (mainly text and graphic images) only in terms of how it is to be displayed and interacted with. For example, the letter "p" placed within markup tags starts a new paragraph.

 XML describes the content in terms of what data is being described. For example, the word "phonenum" placed within markup tags could indicate that the data that followed was a phone number. This means that an XML file can be processed purely as data by a program or it can be stored with similar data on another computer or, like an HTML file, that it can be displayed. For example, depending on how the application in the receiving computer wanted to handle the phone number, it could be stored, displayed, or dialed.

XML is "extensible" because, unlike HTML, the markup symbols are unlimited and self-defining.  It is expected that HTML and XML will be used together in many Web applications. XML markup, for example, may appear within an HTML page. (1) 

XSL:  XSL (Extensible Stylesheet Language), formerly called Extensible Style Language, is a language for creating a style sheet that describes how data sent over the Web using the Extensible Markup Language (XML) is to be presented to the user.  For example, in an XML page that describes the characteristics of one or more automobiles for an insurance company, a set of open and close tags might contain the name of an auto manufacturer. Using XSL, you could tell the Web browser that the auto manufacturer name should be displayed, where to display it on a page, and that it should be displayed in a bold font.

Think of an XML page as similar to an HTML (basic Web) page, but containing data in identified fields rather than text and graphics. XSL gives a developer the tools to describe exactly which data fields in an XML file to display and exactly where and how to display them. Like any style sheet language, XSL can be used to create a style definition for one XML document or reused for many other XML documents.  (1)

Zip:  Zipping is the act of packaging a set of files into a single file or archive that is called a zip file. Usually, the files in a zip file are compressed so that they take up less space in storage or take less time to send to someone. There are several popular tools that can be used for zipping files: WinZip and Netzip for Windows, MacZip for Macintosh users, and Zip and UnZip for UNIX systems. The result of zipping is a single file with a ".zip" suffix. After you receive a zip file, you may have to extract and decompress the file by using the same kind of tool that was used to zip the original file.

Most software that you download from the Internet will arrive as a self-extracting zip file. Typically, by double-clicking on a self-extracting zip file, it will automatically extract, decompress, and store the individual files. One of these files is usually called the "setup.exe" file. Double-clicking on this file will cause the software to be installed as a selectable program in your operating system.  (1)

Television Terminology 

Analog:  Analog technology refers to electronic transmission accomplished by adding signals of varying frequency or amplitude to carrier waves of a given frequency of alternating electromagnetic current. Broadcast and phone transmission have conventionally used analog technology.

Analog also connotes any fluctuating, evolving, or continually changing process. Analog is usually represented as a series of sine waves. The term originated because the modulation of the carrier wave is analogous to the fluctuations of the voice itself.

A modem is used to convert the digital information in your computer to analog signals for your phone line and to convert analog phone signals to digital information for your computer. (1)

ATV:  ATV (Advanced Television) is the name given by the U.S. Federal Communications Commission to digital TV (DTV), the use of digital transmission of video and audio information on broadcast channels and cable TV. ATV includes both high-definition television (HDTV), a format for digital video compression, transmission, and presentation and also the creation of additional channels on the current analog 6 MHz channel. (1)

Advanced Television Enhancement Forum (ATVEF):  A consortium of broadcast, cable and computer companies founded in 1998 that developed the ATVEF Enhanced Content Specification, an HTML and JavaScript-based format for adding content to interactive TV. ATVEF closed at the end of 1999 and turned over the specification to the ATV Forum and SMPTE.  In its short year and a half history, ATVEF compiled a collection of intellectual property from its members about interactive TV that provides a wealth of information about content creation and distribution. After ATVEF's closing, this technology continued to be made available from ATVEF Licensing LLC in Boulder, CO. (2) 

Advanced Television Systems Committee (ATSC):  The Advanced Television Systems Committee (ATSC) is a standards organization that was created in 1982 as part of ATV to promote the establishment of technical standards for all aspects of advanced television systems. Based in Washington, D.C., ATSC has an international membership of over 200 organizations (up from an original 25), including broadcasters, motion picture companies, telecommunications carriers, cable TV programmers, consumer electronics manufacturers, and computer hardware and software companies.   The ATSC developed standards for digital television (DTV) that specify technologies for the transport, format, compression, and transmission of DTV in the U.S. ATSC DTV Standards include digital high definition television HDTV), standard definition television (SDTV), data broadcasting, multichannel surround-sound audio, and satellite direct-to-home broadcasting. For SDTV and HDTV, ATSC chose >MPEG-2 for video, and Dolby Digital for audio. The ATSC is currently finalizing DTV standards for satellite services, conditional access (methods, such as encryption or electronic locking systems, used to restrict service access to authorized users), datacasting, and interactive services.

ATSC standards are expected to revolutionize the television industry as defined by the National Television Standards Committee (NTSC) standards set in 1953. ATSC standards for HDTV are currently being adopted internationally.  (1)

Back channel:   A means of communication from users to content providers. At the same time that content providers are transmitting interactive television (analog or digital) to users, users can connect through a back channel to a Web site--for example, for the original content provider or an advertiser. The back channel can be used to provide feedback, purchase goods and services, and so on. A simple type of back channel is an Internet connection using a modem. (4)

 Cable Head-End:  A cable head-end is the facility at a local cable TV office that originates and communicates cable TV services and cable modem services to subscribers. In distributing cable television services, the head-end includes a satellite dish antenna for receiving incoming programming. This programming is then passed on to the subscriber. (Cable TV companies may also play videotapes and originate live programming.) Normally, all signals are those that are sent downstream to the subscriber, but some are received upstream such as when a customer requests a pay-per-view program.

When a cable company provides Internet access to subscribers, the head-end includes the computer system and databases needed to provide Internet access. The most important component located at the head-end is the Cable Modem Termination System (CMTS), which sends and receives digital cable modem signals on a cable network and is necessary for providing Internet services to cable subscribers.  (1)

Cliff Effect:   When approaching the fringes of reception, analog TV pictures begin to degrade by becoming "snowy." By contrast, when in a weak digital signal area, a relatively small change in received power may cause the DTV picture to abruptly change from perfect to nothing; hence the name, "cliff effect." (5)

Conditional access:   Digital television signals can be scrambled in such a way that they cannot be understood by a conventional decoder. Only when unscrambled by a special system can the original pictures be seen by the viewer. By controlling the operation of the de-scrambling system through the use of a pre-paid access card, or by a transmitted code, the broadcaster can control access to a particular channel or service. Conditional access can be used to control many things from pay-per-view subscription through to target viewing areas. The ATSC specification, at press time, was not complete. (4)

Convergence:  In information technology, convergence is a term for the combining of personal computers, telecommunication, and television into a user experience that is accessible to everyone. In the U.S., an estimated 30% of homes have computers with modems. Virtually, 100% of homes have a TV set. Studies show a large populace of TV users who would embrace the Internet, video-on-demand, and greater interaction with content, but who are diffident about buying and using a personal computer. For these reasons, both the computer and the television industries are embarked on bringing digital TV and the Internet to a larger market.

Convergence is not simply an issue of technology, but also of culture and life style. In general, TV is visual, not very interactive (except for changing channels), oriented primarily toward entertainment and news. Displays are large and TVs are easy to operate, requiring almost no education to use. Personal computers, in spite of their graphical user interfaces (GUI) tend to be more text-oriented, highly interactive, oriented in terms of purpose and content toward business and education uses. Displays are smaller. Computers can be very challenging to use and usually require formal education or a certain personal learning curve.

Convergence is already underway with WebTV, which pipes the World Wide Web to a slightly-modified TV set with a set-top box from an ordinary phone line and provides a degree of interactivity. A number of interactive games designed for the TV environment can also be played over the Internet. Broadcasting companies such as NBC have partnered with computer companies such as Microsoft for TV program content.

A major barrier to more rapid convergence is the large investment required to bring cable TV to households, both by cable access providers and individual households. Satellite wireless service is another approach that is only beginning to bring its subscribers access to the Internet. Digital Subscriber Line (DSL) technologies offer the possibility of sufficient bandwidth connections over ordinary phone wires for streaming video to TV sets.

A consortium of leading computer and telecommunication companies including Compaq, IBM, and Microsoft are working toward common standards that will help speed up convergence and hope to sponsor a standard for a relatively low-cost digital TV. They have endorsed a subset of the recommendations of the Advanced Television System Committee (ATSC) that would speed up a transition to digital TV and so that personal computers could have the ability to receive digital video and data.  (1)

Datacasting:  While broadcasting in HDTV or multicasting in SDTV, digital technology allows broadcasters to use leftover bandwidth to transmit additional program material or non-program related resources, such as video, audio, text, graphics, maps and services, to specially equipped computers, cache boxes, set-top boxes, or DTV receivers. This is called datacasting. DTV's broader bandwidth channel allows information to be downloaded at a transmission rate currently 600 times that of a personal computer modem. (5)

DBS:   Digital broadcast system. An alternative to cable and analog satellite reception initially utilizing a fixed 18-inch dish focused on one or more geostationary satellites. DBS units are able to receive multiple channels of multiplexed video and audio signals as well as programming information, Email, and related data. DBS typically uses MPEG-2 encoding and COFDM transmission. Also known as digital satellite system. (4)

Digital TV:  Digital television (DTV) is the transmission of television signals using digital rather than conventional analog methods. Analog transmission is in the form of a constantly variable wave; digital transmission consists of an electrical pulse which has two possibilities: on and off (or positive and negative), which are represented by a one and a zero (this is binary data, the same type of information that a computer understands). Because a digital signal does not fluctuate, but is either perfectly intact or totally absent, a digital transmission is more precise than an analog transmission. Although both signals are transmitted in the same basic way and have the same range, they behave differently at the limits of their ranges. An analog signal degrades over distance and may be barely detectable at the farther reaches of the broadcast area - this is why the signal from a distant radio station fades in and out. As the signal reaches the farther limits of its range, the signal-to-noise ratio (SNR) decreases and the quality of the broadcast suffers, although the range remains the same. In comparison, when the SNR decreases in a digital signal, the quality of the broadcast does not degrade, but the range shrinks (this is called the cliff effect).

Advantages of DTV over analog TV include:

·         Superior image resolution (detail) for a given bandwidth

·         Smaller bandwidth for a given image resolution

·         Compatibility with computers and the Internet

·         Interactivity

·         Superior audio quality

·         Consistency of reception over varying distances

·         Capacity for multicasting (1)

DTT:   Digital terrestrial television. The term is used in Europe to describe the broadcast of digital television services using terrestrial frequencies. (4)

DVD:  DVD (digital versatile disc) is an optical disc technology that is expected to rapidly replace the CD-ROM disc (as well as the audio compact disc) over the next few years. The digital versatile disc (DVD) holds 4.7 gigabyte of information on one of its two sides, or enough for a 133-minute movie. With two layers on each of its two sides, it will hold up to 17 gigabytes of video, audio, or other information. (Compare this to the current CD-ROM disc of the same physical size, holding 600 megabyte. The DVD can hold more than 28 times as much information!)

DVD-Video is the usual name for the DVD format designed for full-length movies and is a box that will work with your television set. DVD-ROM is the name of the player that will (sooner or later) replace your computer's CD-ROM. It will play regular CD-ROM discs as well as DVD-ROM discs. DVD-RAM is the writeable version. DVD-Audio is a player designed to replace your compact disc player.

DVD uses the MPEG-2 file and compression standard. MPEG-2 images have four times the resolution of MPEG-1 images and can be delivered at 60 interlaced fields per second where two fields constitute one image frame. (MPEG-1 can deliver 30 noninterlaced frames per second.) Audio quality on DVD is comparable to that of current audio compact discs.  (1)

Electronic Program Guide:  An electronic program guide (EPG) is an application used with digital set-top boxes and newer television sets to list current and scheduled programs that are or will be available on each channel and a short summary or commentary for each program. EPG is the electronic equivalent of a printed television program guide.

An EPG is accessed using a remote control device. Menus are provided that allow the user to view a list of programs scheduled for the next few hours up to the next seven days. A typical EPG includes options to set parental controls, order pay-per-view programming, search for programs based on theme or category, and set up a VCR to record programs. Each digital television (DTV) provider offers its own user interface and content for its EPG. (1)

Enhanced Television:  Term used for certain digital on-air programming (usually educational) that includes additional resources downloaded to viewers. Viewers will be able to simultaneously watch an enhanced TV production and, in the background, receive hundreds of megabytes of additional video, audio, text, images and other data related to the program. Some forms of enhanced TV allow live interaction; other forms are not visible on-screen until later recalled by viewers. Enhanced television (also known as "datacasting" or "interactive television") is still based on a broadcast technology, meaning that one source sends out information to many recipients. Users can only interact with the content provider directly when there is a back channel. (5)

Enhancements:   Producers add these to interactive and digital television, as well as other digital content to enhance program material. Examples are supplementary text and graphics that add more depth and richness, or links to reach a Web site, as is done using TV Crossover Links. In analog, the vertical blanking interval (VBI) is used to broadcast enhancements, while in digital, the enhancements are part of the ATSC MPEG-2 stream. Enhancements can be created using industry-standard tools and technologies, like HTML and the ECMA Internet Scripting. (4)

High Definition (HD):  HDTV (high definition television) is a television display technology that provides picture quality similar to 35 mm. movies with sound quality similar to that of today's compact disc. Some television stations have begun transmitting HDTV broadcasts to users on a limited number of channels. HDTV generally uses digital rather than analog signal transmission. HDTV and standard definition television (SDTV) are the two categories of display formats for digital television (DTV) transmissions, which are becoming the standard.

HDTV provides a higher quality display with a vertical resolution display from 720p to 1080i. The p stands for progressive scanning, which means that each scan includes every line for a complete picture, and the i stands for interlaced scanning which means that each scan includes alternate lines for half a picture. These rates translate into a frame rate of up to 60 frames per second, twice that of conventional television. One of HDTV's most prominent features is its wider aspect ratio (the width to height ratio of the screen) of 16:9, a development based

on research showing that the viewer's experience is enhanced by screens that are wider. HDTV pixel numbers range from one to two million, compared to SDTV's range of 300,000 to one million. New television sets will be either HDTV-capable or SDTV-capable, with receivers that can convert the signal to their native display format.

In terms of audio quality, HDTV receives, reproduces, and outputs Dolby Digital 5.1.

HDTV uses the MPEG-2 file format and compression standard. (1)

Interactive TV:  Interactive TV (ITV) is television that allows the viewer to interact with the television set in ways other than simply controlling the channel and the volume and handling videotapes. Typical interactive TV uses are selecting a video film to view from a central bank of films, playing games, voting or providing other immediate feedback through the television connection, banking from home, and shopping from home.

Interactive TV involves adding a special set-top box to the existing television set. In addition, other installation and infrastructure arrangements are required, depending on the particular approach. Most services involve offering special programming, news, and home shopping and a number offer video-on-demand and home banking. An early form of interactive TV is provided by companies that offer Personal Video Recorder services.  (1)

Multicasting:  Because digital television allows you to pack much more information into the allotted signal, we can transmit multiple channels on the same bandwidth instead of just one. Think of a broadcasting bandwidth as a multi-lane freeway. You can run a big, flashy, wide-load truck carrying HDTV and take up all of the lanes, or you can send multiple compact cars down the same freeway, each carrying specialized programming. (5)

Multiplex: 1. To transmit two or more signals at the same time or on the same carrier frequency. 2. To combine two or more electrical signals into a single, composite signal, such as ATSC multicasting. (4)

Multiplexer: Device for combining two or more electrical signals into a single, composite signal. (4)

NTSC:   National television system committee. The organization that developed the analog television standard currently in use in the U.S., Canada, and Japan. Now generally used to refer to that standard. The NTSC standard combines blue, red, and green signals modulated as an AM signal with an FM signal for audio. (4)

Open Cable:  A project aimed at obtaining a new generation of set-top boxes that are interoperable. These new devices will enable a new range of interactive services to be provided to cable customers. (4)

Pay-Per-View:  The number of households with access to digital cable service is expected to grow to 23 million over the next few years. One result for this phenomenal next wave of growth is that PPV revenue is projected to top $2.5 billion by 2005. According to Paul Kagan Associates, 60 percent of these revenues will come from digital hit movies alone.

On the Web, micropayment is a business concept whose goal is to generate revenue by offering pay-per-view Web pages, Web links, or Web services for small amounts of money called "microcents". Since it is not practical for individual users to charge small amounts of money (such as a penny or a fraction of a penny) to a major charge card, a different method of payment is needed for sites that wish to go "micro". Several methods of micropayment collection are being examined, many of which involve encoding per-fee-links inside HTML pages and some kind of Internet wallet account where individuals would establish a cash balance with a third-party application that would monitor, collect, and distribute micropayments.

Once a common micropayment standard has been established, some visionaries predict that streaming media sites, sports access sites, and other specialized resources will pave the way for pay-per view Web use, just as they did for cable TV.  (1)

PSIP: Program and system information protocol. A part of the ATSC digital television specification that enables a DTV receiver to identify program information from the station and use it to create easy-to-recognize electronic program guides for the viewer at home. The PSIP generator insert data related to channel selection and electronic program guides into the ATSC MPEG transport stream. (4)

PVR:  A personal video recorder (PVR) is an interactive TV recording device, in essence a sophisticated set-top box with recording capability (although it is not necessarily kept on top of the television set). Vendors and media also refer to the units by these names: digital video recorder (DVR); personal TV receiver (PTR); personal video station (PVS); and hard disk recorder (HDR).

Like the familiar VCR, a PVR records and plays back television programs, but, unlike the VCR, it stores the programs in digital (rather than analog) form. Like a VCR, a PVR has the ability to pause, rewind, stop, or fast-forward a recorded program. Because the PVR can record a program and replay it almost immediately with a slight time lag, what seem to be live programs can be manipulated as though they were recorded programs (which they actually are). A PVR's capabilities include time marking, indexing, and non-linear editing. The PVR encodes an incoming video data stream as MPEG-1 or MPEG-2 and stores it on a hard disk within a device that looks much like a VCR.

Most PVRs come as part of a subscriber service that may or may not charge a monthly fee. The service enables such activities as searching for shows according to type (movies or baseball games, for example), choosing among video-on-demand (VOD) options, or doing shopping or banking. Service providers, such as TiVo and ReplayTV, may also sell PVRs. There are a number of PVRs on the market, including TiVo's DVR, SONICblue's ReplayTV, Sony's SVR-2000, and Philips' PTR. There are also products that offer similar functionality but are software-based (such as SnapStream Personal Video Station) or network-based. The Digital Video Broadcasting (DVB) Project is an industry consortium dedicated to the development of standards for PVRs and other digital video technologies.  (1)

Resolution: 1. Detail. In digital video and audio, the number of bits (four, eight, 10, 12, etc.) determines the resolution of the digital signal. Four bits yields a resolution of one in 16. Eight bits yields a resolution of one in 256. Ten bits yields a resolution of one in 1,024. Eight bits is the minimum acceptable for broadcast television. 2. A measure of the finest detail that can be seen, or resolved, in a reproduced image. While influenced by the number of pixels in an image (for high definition approximately 2,000 x 1,000, broadcast NTSC TV 720 x 487, broadcast PAL TV 720 x 576), note that the pixel numbers do not define ultimate resolution but merely the resolution of that part of the equipment. The quality of lenses, display tubes, film process and film scanners, etc., used to produce the image on the screen must all be taken into account. This is why a live broadcast of the Super Bowl looks better than a broadcast recorded and played off of VHS, while all are NTSC or PAL. (4)

Set Top Box:  A set-top box is a device that enables a television set to become a user interface to the Internet and also enables a television set to receive and decode digital television (DTV) broadcasts. DTV set-top boxes are sometimes called receivers. A set-top box is necessary to television viewers who wish to use their current analog television sets to receive digital broadcasts. It is estimated that 35 million homes will use digital set-top boxes by the end of 2006, the estimated year ending the transition to DTV.

In the Internet realm, a set-top box is really a specialized computer that can "talk to" the Internet - that is, it contains a Web browser (which is really a Hypertext Transfer Protocol client) and the Internet's main program, TCP/IP. The service to which the set-top box is attached may be through a telephone line as, for example, with WebTV, or through a cable TV company like TCI.

In the DTV realm, a typical digital set-top box contains one or more microprocessors for running the operating system, possibly Linux or Windows CE, and for parsing the MPEG transport stream. A set-top box also includes RAM, an MPEG decoder chip, and more chips for audio decoding and processing. The contents of a set-top box depend on the DTV standard used. More sophisticated set-top boxes contain a hard drive for storing recorded television broadcasts, for downloaded software, and for other applications provided by your DTV service provider.

Digital television set-top boxes are used for satellite, cable, and terrestrial DTV services. They are especially important for terrestrial services because they guarantee viewers free television broadcasting. A set-top box price ranges from $100 for basic features to over $1,000 for a more sophisticated box. It is often leased as part of signing up for a service.  (1)

Standard Definition TV:  Standard definition television (SDTV) is a digital television (DTV) format that provides a picture quality similar to digital versatile disk (DVD). SDTV and high definition television (HDTV) are the two categories of display formats for digital television (DTV) transmissions, which are becoming the standard.

Because a compressed SDTV digital signal is smaller than a compressed HDTV signal, broadcasters can transmit up to five digital SDTV programs simultaneously instead of just one HDTV program. This is multicasting. Multicasting is an attractive feature because television stations can receive additional revenue from the additional advertising these extra programs provide. With today's analog television system, only one program at a time can be transmitted.

When the United States decided to make the transition from analog television to DTV, the Federal Communications Commission decided to let broadcasters decide whether to broadcast SDTV or HDTV programs. This is still being decided by most of the broadcasters in the United States.  Both SDTV and HDTV are supported by the Digital Video Broadcasting (DTV) and Advanced Television Systems Committee (ATSC) set of standards.  (1)

Video On Demand:  The ability to start delivering a movie or other video program to an individual Web browser or TV set whenever the user requests it. (2)

WebTV:   WebTV Networks, Inc. is a leading manufacturer of set-top boxes used for viewing interactive television and regular television. These receivers let users access the Internet, including use of electronic mail and online chats. WebTV set-top boxes like the WebTV Plus Receiver connect to a standard television and a phone line. The WebTV Plus Receiver supports TV Crossover Links and WebPIP. WebPIP lets users simultaneously view Web pages and TV programming on the same screen, without a special picture-in-picture TV. WebTV is a trademark and service of the Microsoft Corporation. (4)

Notes on Sources:

(1)   Adapted from Tech Target Network’s “Whatis.com” www.techtarget.com

(2)   Adapted from United Business Media’s “Tech Encyclopedia” www.techweb.com

(3)   Adapted from Internet.com’s “Webopedia” www.pcwebopaedia.com

(4)   Adapted from Dish Network’s “Digital TV.com” www.digitaltv.com

(5)   Adapted from KCTS’s “Digital TV Glossary” www.kcts.org