XML

The Extensible Markup Language (XML) is a recommended general-purpose mark-up language for creating special-purpose mark-up languages, capable of describing many different kinds of data. Its primary purpose is to facilitate the sharing of data across different systems, particularly systems connected via the Internet. *instinctools GateOne Framework is XML enabled.

XML provides a text-based means to describe and apply a tree-based structure to information. At its base level, all information manifests as text, interspersed with mark-up that indicates the information's separation into a hierarchy of character data, container-like elements, and attributes of those elements. The general syntax of such languages is rigid - documents must adhere to the general rules of XML, assuring that all "XML-aware" software can at least read (parse) and understand the relative arrangement of information within them. With XML, it is much easier to write software that accesses the document's information, since the data structures are expressed in a formal, relatively simple way.

Some features of XML which make it well-suited for data transfer are:

• its simultaneously human- and machine-readable format;
• it has support for Unicode, allowing almost any information in any human language to be communicated;
• the ability to represent the most general data structures: records, lists and trees;
• the self-documenting format that describes structure and field names as well as specific values;
• the strict syntax and parsing (reading) requirements that allow the necessary parsing algorithms to remain simple, efficient, and consistent. XML is also heavily used as a format for document storage and processing, both online and offline, and offers several benefits:
• its robust, logically-verifiable format is based on international standards;
• the hierarchical structure is suitable for most (but not all) types of documents;
• it manifests as text files, unencumbered by licenses or restrictions;
• it is platform-independent, thus relatively immune to changes in technology;
• it and its predecessor, SGML, have been in use since 1986, so there is extensive experience and software available.

XML allows separating form from content. XML file contains document information (text, data) and identifies its structure: formatting and other processing needs are identified separately in a style sheet or processing system. The two are combined at output time to apply the required formatting to the text or data identified by its structure (location, position, rank, order, or whatever).

For certain applications, XML also has the following weaknesses:

Its syntax is fairly verbose and partially redundant. This can hurt human readability and application efficiency, and yields higher storage costs. It can also make XML difficult to apply in cases where bandwidth is limited, though compression can reduce the problem in some cases.

Uses of XML

• Information identification. Meaningful names for all information items can be defined since "mark-up" is created by users themselves.
• Information storage. Since XML is portable and non-proprietary, it can be used to store textual information across any platform. Because it is backed by an international standard, it still can be accessed and processed as a data format.
• Information structure. XML can therefore be used to store and identify any kind of hierarchical information structure, especially for long, deep, or complex document sets or data sources, making it ideal for an information-management back-end to serving the Web. This is its most common Web application.
• Publishing. Combining the three previous topics (identity, storage and structure) it is possible to get all the benefits of robust document management and control (with XML) and publish to the Web (as HTML) as well as to paper (as PDF) and to other formats (eg Braille, Audio, etc) from a single source document by using appropriate style sheets.
• Messaging and data transfer. XML is also very heavily used for enclosing or encapsulating information in order to pass it between different computing systems which would otherwise be unable to communicate.
• Web services. Building on all of these, as well as its use in browsers, machine-processible data can be exchanged between consenting systems, where before it was only comprehensible by humans (HTML). Weather services, e-commerce sites, blog, news_feeds, AJaX sites, and thousands of other data-exchange services use XML for data management and transmission, and the web browser for display and interaction.