dictionary of multimedia and internet applications: a guide for developers and users. francis botto

Print ISBN 0-471-98624-0 Online ISBN 0-470-84178-8

AAAS (American Association for the Advancement of Sciences) An American organisation dedicated to the sciences.

AAIM (Association for Applied Interactive Multimedia) An organisation

that serves multimedia professionals.

(See www.aaim.org)

Abel, Robert A pioneering multimedia author. His early works include

Guernica, an interactive documentary about the destruction of the Basque Town of the same name during the Spanish Civil War. Picasso’s famous painting Guernica is used to promote the central theme. Guernica was initially platformed on the Apple Macintosh computer.

Absolute addressing A method of addressing stored information, where

addresses are independent of one another. CD-ROM block addresses include measurements of time and data blocks read. Minutes, seconds and blocks provide enough information to locate information. For example, a one-hour CD-ROM would use the addressing scheme:

● Minutes (M): 0–59

● Seconds (S): 0–59

● Blocks (B): 0–74

A track beginning midway through the CD-ROM might be addressed 29:29:37 (M:S:B). This addressing technique is also reflected in CD-I. (See CD-ROM and DVD.)

Accelerator 1. A graphics card offering high-speed operation and

optimised for GUIs such as the X Window system, Windows and OS/2. (See 3-D and Graphics card.) 2. A video accelerator is a graphics card that is able to speed up the playback frame rate of video sequences. The acceleration is achieved by inserting duplicate frames. VideoLogic was one of the first companies to demonstrate the acceleration of Windows .AVI video files using this technique. (See MPEG*.)

Acceptance cone

Acceptance cone A range of angles at which a laser beam may be injected into a fibre optic cable so that the ray is propagated for the entire fibre’s length. It is a function of the numerical aperture (NA), which is greater with multi-mode fibres than it is with mono- or single-mode fibres.

(See Optical fibre.)

Access A process by which users gain the rights to operate a local or remote system, application or program. The user may be required to enter an ID and password.

(See Encryption and Security.)

Access technology A method used to connect to the Internet or to a remote network or computer system. Access technologies include:

● PSTN and analogue modem offering speeds up to 56.6 Kbps ● analogue and digital GSM

● ISDN

● Cable

● DSL

● ADSL

● GSM

● DBS (Direct Broadcast Satellite) (See 56.6 Kbps, ADSL, ATM, B-ISDN, Cable modem, ISDN and Modem.)

Access time The interval between a data request and data retrieval. Hard disk and CD-ROM access times are measured in milliseconds (ms) (or thousandths of a second.) The length of access time depends largely on the electromechanical architecture, but increasingly controllers play an import-ant role. For instance, hard disk cache controllers may reduce the measured disk access time to tenths of a millisecond. In the perspective of DVD and CD-ROM, average access time is the time taken for the laser head to locate and begin reading an appropriate region of the disc. Access time tends to increase with turns of track that are farthest from the disc’s centre.

(See CD-ROM, DVD and Hard disk.)

Accumulator The part of a processor architecture that can be used to store the results of arithmetic operations. It consists of one or more registers, and its overall size often indicates the size of instructions that can be processed.

(See Processor.)

ACID (Atomicity, Consistency, Isolation and Durability) A series of properties which define the real-world requirements for transaction processing (TP).

Active Control Pad

Atomicity A process of ensuring that each transaction is a single workload unit.

If any subaction fails, the entire transaction is halted and rolled back.

Consistency A process of ensuring that the system is left in a stable state. If this

is not possible the system is rolled back to the pre-transaction state.

Isolation A process of ensuring that system state changes invoked by one

running transaction do not influence another running transaction. Such

changes must only affect other transactions when they result from completed

transactions.

Durability A process of guaranteeing that the system state changes of a

transaction are involatile, and impervious to total or partial system failures.

(See Server and Transaction.)

Acoustic coupler A device that may be fitted to a telephone handset,

enabling data communications.

Acrobat (See Adobe Acrobat.)

ActionMedia II An i750 chipset-based graphics card that can play video

compressed according to the Intel Indeo video standard. It is an evolved version of the original i750-based ActionMedia board developed to play and record video according to the Intel Digital Video Interactive (DVI) technology. Two ActionMedia DVI boards were required: one for playback and another for video capture and compression. DVI was a notable mile-stone in the development of the PC as a multimedia device and in the evolution of digital video in the PC environment.

(See DVI and MPEG*.)

Active Channels A connection to a Web site which sees information

pushed to the Windows Active Desktop.

(See Active Desktop.)

Active Control Pad A development tool which may be used to develop

interactive Web pages. It supports JScript and VBScript, and can be used to integrate ActiveX controls. The program is supplied with a number of user interface-related ActiveX controls, which include:

● Forms 2.0 Label for creating labels on Web pages ● Forms 2.0 Text Box

● Forms 2.0 Combo Box

● Form 2.0 List Box

Active Desktop

● Forms 2.0 Check Box

● Forms 2.0 Option Button

● Forms 2.0 Toggle

● Forms 2.0 CommandButton

(See Active Desktop, Active Document, ActiveX*, Java, JavaScript, VBScript and Visual Basic.)

Active Desktop 1. A term used to describe the client side of an Active Web application, and to describe the addition of Active Desktop Components (ADCs) to the Windows Desktop. The Web page uses ActiveX scripting (with VBScript or JScript) in order to integrate and coordinate:

● Active Desktop Components (ADC) ● HTML code

● ActiveX controls

● Java Applets.

(See Active Desktop Component, Active server, ActiveX control, Java, JScript, OLE, VBScript and Visual Basic.) The integration of Web browsing capabilities in the Windows 95 or 98 Desktop. It is intended to provide the user with seamless connection to, and use of, the Internet. Whether applications and data are local or remote (i.e. on the Internet or an intranet) is transparent to the user. Active Desktop Compondents (ADCs) are arranged on the desktop in the form of Active Channels, and offer various functions. Connectivity to Web sites is provided by Active Channels in the form of Channel bars, which may be selected from the Windows Desktop.

Active Desktop Component (ADC) A component, which might be an ActiveX control, that is integrated into an Active Desktop. For instance, the PointCast ADC is an example, and may be configured to receive selected information from news services.

(See Active Desktop.)

Active document A term which describes the integration of Internet Explorer with documents. For instance, Microsoft Office documents might be opened using Internet Explorer.

(See Microsoft Office.)

ActiveMovie A Microsoft streaming video technology which is integrated in Internet Explorer. It supports the video formats QuickTime, MPEG and AVI.

(See ASF and www.microsoft.com/imedia.)

Active window

Active server A server that pushes data to a client’s Active Desktop and

delivers Active Channels. Server-side application components are common in type to the Active Desktop. These may include:

● ActiveX controls

● Java applets

● JScript

● VBScript

● HTML.

The server-side implementation may integrate the MCIS server components.

(See ASP, Java, JScript, MCIS, OLE, VBScript and Visual Basic.)

Active Server Components (See ASP.)

Active Server Page (ASP) (See ASP.)

Active Template Library (ATL) A development tool used to develop Active Server Components, which may be in-process or out-process.

(See ASP.)

Active Web Architecture An architecture which provides bi-directional

information flow between the HTTP server and HTTP client. The resulting interactivity on the client side permits data entry and the editing of HTML documents. It uses the Common Gateway Interface (CGI) between the HTTP server and its applications and databases. CGI is a protocol which provides the necessary communications. CGI scripts are created using a scripting language or programming tool. (See Figure on page 22).

(See CGI and Perl.)

Active window A window which is currently selected by the user. The window might be activated when the user:

● clicks on the window

● selects its related application button from the Taskbar ● selects the window from the Window menu ● selects the window using the keyboard by pressing Alt-Esc, or by

pressing Alt-Tab.

(See Windows.)

ActiveX control An object or component that adds functionality to an application which may be standalone or deployed over the Web or network. Microsoft ActiveX is an object architecture based on OLE 2.0, and is intended for deployment over the Internet and compatible IP networks.

ActiveX control

HTTP

Applications Database

CGI Server CGI

IP network Client

Internet or Intranet

Client Client

Browser

Client

Active Web

More accurately, ActiveX is a reincarnation of OCX and may use COM and DCOM as glues. ActiveX provides cost-effective functionality gains for Web browsers. An ActiveX control might take the form of a streaming video player, or a streaming audio player that might be added to Internet Explorer (which is a Web browser). ActiveX controls may be created using Visual C++, Visual Basic 5 Control Creation Edition or Java.

Guidelines for creating ActiveX controls

● Refer to existing active controls in the public domain, to those that are

shareware, and to those that might be conventionally marketed and sold. The economics of recreating that which has already been created might prove undesirable. Study the functionality of the ActiveX controls and try to obtain real-world reviews of them, in order to gain an understanding of what may be expected from them.

● Use the latest editions of development tools such as Visual Basic Control

Edition and Visual Studio.

● Supply detailed design, architecture, implementation and functionality docu-

mentation. If the ActiveX control may be modified at the code level, provide adequate comments in the source listing. Also include an impact statement of how the ActiveX control changes targeted applications, together with reusing a strategy of useful code segments or algorithms designed.

● Do not intentionally integrate patented algorithms in your ActiveX control. It

ActiveX scripting

is accepted that such infringements can be implemented unwittingly by the developer/programmer.

● Test the ActiveX control.

● Provide case scenarios giving real-world examples of their integration in Web

applications.

● Refer to Microsoft’s Web site for the latest ActiveX specification and

development tools.

● Integrate configuration features which may be used from within the application

where the ActiveX control is embedded.

● State the development environments/tools with which the ActiveX control has

been tested.

(See Authenticode.)

ActiveX components running on the same system may interact using the COM protocol as a glue. Industry-wide support beyond Microsoft in ActiveX-compatible development tools includes:

● Borland Delphi

● Powersoft PowerBuilder (See www.powersoft.com) ● Powersoft Optima++ (See www.powersoft.com) ● Symantec C++ (See www.symantec.com) ● MetroWerks Code Warrior (See www.metrowerks.com).

(See Active Desktop, Active document, Active server, Authenticode, COM, DCOM, Glue, HTML, Java and Visual Basic.)

ActiveX scripting A process by which ActiveX controls and Java Applets

may be integrated into the underlying HTML code of an interactive Web application. Such scripting is generally used with Web applications, though standalone applications may also be built using the same. The scripting languages JScript and VBScript are used widely. A basic HTML listing may be given functionality and responses to events through:

● JScript code

● VBScript code

● ActiveX Controls such as Shockwave and multimedia streaming

components

● Java applets.

Such a development strategy can be used to give the client-side a level of intelligence. Validations of user data and interactions distribute processing away from the server-side. This lessens the volume of data traffic and serves to optimise application performance. ActiveX scripting may also be applied to the server-side; it is possible to create Active Server Pages (ASPs).

(See ASP, CGI, HTML, Java, Java applet, JavaScript, Shockwave, VBScript.)

ActiveX SDK

ActiveX SDK (Software Development Kit) A programming tool for creating ActiveX controls. ActiveX controls can also be produced using:

● C++

● Java

● Visual Basic.

(See ActiveX control, Java* and Visual Basic.)

ActiveX security A term used to describe the filtering of unwanted

ActiveX controls or presenting the user with an option to do so.

(See Authenticode and Security gateway.)

ADA A high-level programming language and the namesake of Lord Byron’s daughter, who became the world’s first technical writer in com-puting when documenting Charles Babbage’s mechanical computer.

Adaptive data compression A proprietary data compression technique integrated into the design of many Hayes modems. The algorithm adapts itself so as to optimise compression.

ADC (Analogue to Digital Converter) 1. A device or electronic assembly used to convert continuously varying analogue signals into digital form. The accuracy achieved depends largely on the size of samples and on the sampling rate. Video capture boards and sound cards include analogue to digital converters. Standard PC and Macintosh sound cards tend to record using 8 bit or 16 bit samples at sampling rates of 11.25 kHz, 22.05 kHz or 44.1 kHz. Highly specified sound cards may record using sampling rates of up to 48 kHz, which equates to DAT quality. Video capture cards generally play a dual ADC role, converting audio as well as video into digital form. Normally audio is digitised using the same sample sizes and sampling frequencies available on most fully specified sound cards. Whether capturing from a VHS or S-VHS video source recording, the process of digitising a video signal requires a great deal more com-putation than that of an analogue audio signal. The maximum frame capture rate of a video capture card is a function of its maximum sampling rate, which is linked to the maximum data rate at which it can operate. 2. Active Desktop Component.

(See Active Desktop and Active Desktop Component.)

Address 1. (See IP address.) 2. CD-ROM addresses include measure-ments of time and data blocks read. (See Absolute addressing.) 3. A binary address of data or instructions that are stored in memory. 32 bit software is able to access memory more efficiently than 16 bit variants. It is capable of

Adobe Illustrator

flat memory addressing in which 4 Gbyte (2 32) memory segments can be addressed. A 32 bit segment register is used to point to addresses within a 4 Gbyte range. At the machine code level, the addresses of data and instructions are held in a register called a program counter. Typically its contents grow by increments of one, except when a conditional or unconditional jump occurs to a new memory location. This normally occurs when a subroutine is executed. At such times, the contents of the program counter are placed on a stack, which is a portion of memory that operates according to the LIFO (last in, first out) system. This ensures that the last address placed on the stack is the first to be retrieved. When the subroutine is completed (perhaps using the RET command), the return address is recovered from the stack and placed back into the program counter register.

Address Book A Windows NT-based server which is part of the Microsoft Commercial Internet System (MCIS). (See MCIS.) Address Book allows users to query a database of users, which may include dynamic values such as IP addresses as well as static values that might include names, addresses, age, interests and occupation. It is compatible with:

● NetMeeting, which supports Internet telephony and conferencing ● an Internet Locator server, which may be used to query the database ● a Microsoft SQL Server, which can be used as the database.

(See Internet telephony and Microsoft SQL Server.)

Address bus A unidirectional address bus on a processor. It consists of a

number of lines, and interfaces with memory devices and memory decoders.

Adobe Acrobat An Adobe file format that permits formatted documents to be deployed efficiently over the Web. Adobe Acrobat Reader is required to read Acrobat files (which have the .PDF extension). Using Netscape Navigator, the Acrobat Reader requires a plug-in, while Microsoft Internet Explorer uses an ActiveX control.

(See ActiveX control.)

Adobe After Effects A 2-D/3-D animation program which permits various effects and enhancements.

Adobe Dimensions A 3-D graphics program.

Adobe Illustrator A graphics program used widely for Web and

multimedia production and to originate images for print.

Adobe PageMill

Adobe PageMill A Web site development tool which may be used to develop Web applications.

(See ActiveX control, CGI, Java*, MCIS and Web Server.)

Adobe PhotoShop A program used widely for image manipulation, enhancement and editing.

Adobe Premiere A video editing tool.

(See Multimedia production and Video capture.)

Adobe Streamline A graphics package that provides a number of tools, and can convert images into line drawings.

(See PaintShop Pro.)

ADPCM (Adaptive Delta Pulse Code Modulation) A process by which an analogue signal is converted into digital form. It is a development of Pulse Code Modulation (PCM). The sampling rate influences how accurately sharply varying analogue signals are digitised. It is used in CD-I and many other digital audio, video and multimedia technologies.

ADSL (Asymmetric Digital Subscriber Line) An access technology that

uses the existing copper wire networks that are synonymous with POTS (Plain Old Telephone Services), though these may also include fibre optics. Its downstream bandwidth is considerably wider than its upstream band-width:

● Downstream bandwidth of between 1.5 Mbps and 8 Mbps. Typically it is

1.5 Mbps.

● Upstream bandwidth of the order of 16 to 640 Kbps, which can be a

function of the line length. Typically it is 384 Kbps. ● Line lengths of up to 5 km are quoted. Typically a repeater is required

for distances greater than 1800 feet in order to overcome attenuation.

Applications include:

● high-speed Internet access

● VHS quality videoconferencing ● VoD (video-on-demand)

● multimedia networks

Discrete multitone (DMT) modulation according to ANSI T1.413 separates upstream data from downstream data by separating the signal into separate 43 kHz carrier bands.

(See Access technology.)

AI (artificial intelligence)

Cable VoD

ISP

Television Provider

Downstream, typically 1.5—8 Mbps

Upstream, typically 16—640 Kbps

ADSL modem

Client device

such as

NC, Macintosh,

PC, STB and HIS

ADSL

Aftertouch A keyboard which is sensitive to the firmness of touch, e.g.

musical volume is increased by pressing harder on the key(s).

Agent 1. An agent/manager architecture used for system management in client/server systems. The agents represent managed subjects, which are communicated with and manipulated by managers. 2. A triggered agent is a program that responds to events with appropriate actions. The actions might be little more than answering a telephone call. More sophisticated agents might modify software, build databases or even data warehouses, or add items to a cache, in response to usage habits. Events such as changes to files or directories might also be used as triggers. 3. An habitual agent can be programmed to implement tasks at a precise frequency, such as hourly or daily. 4. A Microsoft ActiveX control intended to enhance the UI of local and Web applications. 5. In a telecommunications network, an agent interprets various commands and responds to them appropriately.

AGP (Accelerated Graphics Port) A high-speed graphics controller implementation which uses a 66 MHz bus. This doubles the speed of PCI cards, which exploit a 33 MHz bus connection. (See Graphics card.)

AI (artificial intelligence) A term used to describe the use of a system to

emulate human decision-making and learning abilities. The founding father