J

Jabber Level: 2 Definition: Sometimes referred to as the “Linux of instant messaging,” Jabber is an open-source platform for developing instant messaging applications. Jabber provides a set of streaming XML protocols and technologies that make it possible for any two entities on the Internet to exchange messages, presence (identifying who is online and where), and other useful information in almost real time. According to the Jabber Software Foundation, the architecture of a Jabber network is similar to e-mail, making it relatively easy for individuals to develop their own instant messaging applications and install and run their own Jabber servers. Jabber also offers the ability to isolate its servers from the public Jabber network, making it possible to develop a closed, more secure instant messaging environment. The Jabber Software Foundation oversees the maintenance of common extensions to ensure interoperability. (See also ICQ and Instant Messaging.)

Jack Level: 1 Definition: In electronics equipment, a jack usually refers to a “female” receptacle that will accept a compatible “male” connector or plug. (See also PSTN.)

Java Level: 2 Definition: Refers to a platform-independent programming language developed by Sun Microsystems in the early 1990s. Java is an object-oriented, secure, robust, general-purpose programming

be used on language for the Internet in the form of “applets” and is used in developing small, specialized computing appliances. The Java approach directly challenges the idea that software must be “installed” and remain resident on a computer to be viable and useful. Not to be confused with JavaScript. (See also Applet, Cross Platform, and Network Computer.)

Java Database Connectivity (See JDBC.)

JavaScript Level: 2 Definition: Netscape’s simple cross-platform scripting language that is widely used to orchestrate enhanced interactivity and advanced functionality in web pages (not to be confused with Java). For example, the popular feature of passing a mouse over a graphic or a button on a web site and having it instantly change color is often achieved through the use of JavaScript. Microsoft began supporting JavaScript in its Internet Explorer browser in the late 1990s. JavaScript can be used to validate entries on a web page form, launch new browser windows, and has many uses outside the Web. ActionScript, the programming language used in Marcomedia Flash, bears a strong resemblance to JavaScript. (See also ActionScript, Cross Platform, and Open Source.)

JBoss Level: 3 Definition: JBoss is an open-source Java-based application server platform that implements the entire J2EE suite of services. It can be used on any operating system that supports Java. (See also Application Server and J2EE.)

JDBC (Java Database Connectivity) Level: 3 Definition: A Java application programming interface, or API (a set of routines, protocols, and tools), that makes it possible for programs written in the Java programming language to interact with

(SQL). on platform, and because SQL is a widely adopted standard for accessing databases, Java applications using JDBC can run in almost any server environment and interact with almost any type of database management system. (See also ODBC, RDMS, and SQL.)

Jitter Level: 2 Definition: Any undesired short duration shift in the intended signal due to a lack of synchronization during transmission. Jitter can be evident in the frequency, phase, amplitude, or timing of an intended signal and can be caused by imperfections in transmission pathway or connection equipment. Jitter can be a common problem for video transmitted on asynchronous networks such as ATM. (See also Jitter Buffer.)

Jitter Buffer Level: 2 Definition: Used in a voice-over-IP (VoIP) telephone conversation, which sends individual packets of voice data over the Internet to enable a telephone conversation, the jitter buffer collects packets of voice data on the receiver end into a shared data area where they can be stored and sent to the voice processor in evenly spaced intervals. Because packets can arrive at different times or out of sequence, a jitter buffer is necessary to pool the packets and process in sequence to ensure that the call can be made with as little distortion as possible. (See also Buffer, Jitter, Packet, and VoIP.)

Joint Photographic Experts Group (See JPEG.)

JPEG (Joint Photographic Experts Group) Level: 2 Definition: Refers to a compression standard endorsed by JPEG that applies to individual frames of still video or pictures. The JPEG standard removes or subtracts redundant information from a frame of digital video in order to compress the signal for computer file storage or to transfer

less been and ISO standards organizations. JPEG compression tends to work best on images that contain millions of colors (such as typical photographs), whereas GIF compression works best on almost every other type of image. (See also Compression, GIF, and Vector Graphics.)

J# Level: 3 Definition: Microsoft’s implementation of the Java programming language (invented by Sun Microsystems). J# (pronounced “jay sharp”) is a cornerstone technology of Microsoft’s .NET platform. (See also Java and .Net.)

J2EE Level: 3 Definition: A competitor to Microsoft’s .NET framework, Sun Microsystem’s J2EE (pronounced “jay two double E”) provides the ability to develop large-scale web-based applications that are delivered via the Internet. Consisting of several components, including Java Server Pages (which produce HTML documents that can be handled with a standard web browser), Java Beans (which provide the server-side functionality used to run complex applications), and connectivity with databases using JDBC (Java database connectivity)—Java’s equivalent of ODBC. (See also Client/Server, JBoss, JDBC, .NET, ODBC, and Web Application.)

Judder Level: 2 Definition: The appearance of minute jerky movements in motion pictures, either because the consecutive film frames are not pulled precisely to the same position in the projector gate or because frame conversion rates do not match.