's Glossary of XML, P2P and Semantic Web-related Terms

Conversational model
CSS (Cascading Style Sheets)
Data Model
Data Typing
Decentralized Network
Document Type Declaration (DOCTYPE declaration)
Document Type Definition (DTD)
HyperText Transfer Protocol (HTTP)
Graphical User Interface (GUI)
Markup Language
Meta-markup language
P2P or Peer-to-peer
Structured Query Language (SQL)

Standard Generalized Markup Language (SGML)
Style sheets
Unified Modeling Language (UML)
Uniform Resource Locator (URL)
Web server
XML Schema
XSL (Extensible Stylesheet Language)
XSLT (XSL Transformations)

Conversational model - a bi-directional communication model taking place across a distributed network. (The three characteristics of a conversation are: that it happens spontaneously, that it is transient (lasts a short time) and that it occurs among a group of (or between two) equal "peers".)

CSS (Cascading Style Sheets) - A W3C Standard that uses a rule-based declarative syntax that assigns formatting properties to the element either HTML or XML element content.

Data Model - A data model is what is formally-defined in a DTD (Document Type Definition) or XML Schema. A document's "data model" consists of the allowable element and attribute names and optional structural and occurrence constraints for a "type" or "class" of documents.

Data Typing - Data is said to be "typed" when it takes on additional abstract meaning than what its characters usually represent. "Integers", "dates", "booleans", and "strings" are all examples of "typed" data (data types). A data value that is typed takes on additional meaning, due to the semantic properties known to be associated with specific named "data types".

Document type declaration (DOCTYPE declaration) - A document type declaration is the syntactical "glue" used by an XML document to locate an external DTD (Document Type Definition) so that it can be validated against it.

Decentralized Network - A computer network distributed across many peers rather than centralized around a server.

Document Type Definition (DTD) - A formal definition of the data model (the elements and attributes allowed and their allowable content and nesting structure) for a class of documents. XML DTDs are written using SGML DTD syntax

HyperLink - see "Link"

HyperText Transfer Protocol (HTTP) - This is the protocol by which web clients (browsers) and web servers communicate. It is stateless, meaning that it does not maintain a conversation between a given client and server, but it can be manipulated using scripting to appear as if state is being maintained. Do not confuse HTML (Markup language for our browser-based front ends), with HTTP (protocol used by clients and servers to send and receive messages over the Web).

Graphical User Interface(GUI) - A GUI is what an end-user sees and interacts with when operating (interacting with) a software application. Sometimes referred to as the "front-end" of an application. HTML is the GUI standard for web-based applications.

Link - A link (or hyperlink) is a relationship between two resources. HTML links usually connect HTML documents together in this fashion (called a "hyperlink"), but links can link to any type of resource (documents, pictures, sound and video files) capable of residing at a Web address (URL).

Markup - Markup is comprised of several "special characters" that are used to structure a document's character data into logical components that can then be labeled (named) so that they can be manipulated more easily by a software application. (Everything in an XML document is either "character data" or "markup".)

Markup Language - A markup language is used to structure a document's character data into logical components, and "name" them in a manner that is useful. These labels (element names) provide either formatting information about how the character data should be visually presented (for a word processor or a web browser, for instance) or they can provide "semantic" (meaningful) information about what kind of data the component represents. Markup languages provide a simple format for exchanging text-based character data that can be understood by both humans and machines.

Meta-markup language - A language used to define markup languages. SGML and XML are both meta-markup languages. HTML is a markup language that was defined using the SGML meta-markup language.

Peer - A conversation participant. An "equal" to whatever person or application it is communicating with across a network (bi-directional communication).

P2P or Peer-to-peer - A blanket term used to describe: (1) a peer-centric distributed software architecture, (2) a flavor of software that encourages collaboration and file sharing between peers, and (3) a cultural progression in the way humans and applications interact with each other that emphasizes two way interactive "conversations" in place of the Web's initial television-like communication model (where information only flows in one direction).

Resource - Anything addressable via a URL. Examples of resources are: documents, files, pictures, sounds, videos and databases.

Structured Query Language (SQL) - An ISO and ANSI standard language for database access. SQL is sometimes implemented as an interactive, command line application and sometimes is used within database applications. Typical commands include select, insert, and update.

Standard Generalized Markup Language (SGML) -Since 1986, SGML has been the international ISO standard used to define standards-based markup languages. HTML is a markup language that is defined using SGML. The HTML DTD the specifies HTML is written in SGML syntax. XML is not a markup language written in SGML. There is no pre-defined DTD for "XML Markup". XML is a subset of the SGML standard itself.

Style sheets- A term extended from print publishing to online media. A style sheet can contain either formatting information (as is the case with CSS - Cascading Style Sheets, or XSL FOs - XSL Formatting Objects), or it can contain information about how to manipulate the structure of a document, so it can be "transformed" into another type of structure (as is the case with XSLT Transformation "style sheets").

Transformation - In XSLT, a transformation is the process of a software application applying a style sheet containing template "rules" to a source document containing structured XML markup to create a new document containing a completely altered data structure.

Unified Modeling Language (UML) - Derived from three separate modeling languages, UML offers a standard for transforming real-world objects and behaviors into a notation from which object-oriented computer programs can be written.

Uniform Resource Locator (URL) - The address of a file or resource on the Internet.

Valid - An XML document is "valid" if it is both well-formed and it conforms to an explicitly-defined data model that has been expressed using SGML's DTD (Document Type Definition) syntax.

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).

Well-formed - A document is "well-formed" if all of its start tags have end tags and are nested properly, with any empty tags properly terminated, and any attribute values properly quoted. An XML document must be well-formed by definition.

XML Schema - A formal definition of a "class" or "type" of documents that is expressed using XML syntax instead of SGML DTD syntax.

XSL (Extensible Stylesheet Language) - XSL has two parts to it: a transformation vocabulary (XSL Transformations - XSLT) and a formatting vocabulary (XSL Formatting Objects (XSL FOs).

XSL FOs - XSL Formatting Objects - The formatting vocabulary part of XSL that applies style properties to the result of an XSLT transformation.

XSLT (XSL Transformations) - The transformation vocabulary part of XSL. An XSLT "stylesheet" contains template rules that are applied to selected portions of a source document's "source tree" to produce a "result tree" that can then be rendered for viewing, processed by another application, or further transformed into another data structure.