What is XML

Asks marmalade

A. XML stands for Extensible Markup Language. It is similar in principle to hypertext markup language (HTML) in tagging information to appear on web pages.

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However, where HTML's markup symbols and tags describe the content of a page in terms of how the content is to be displayed or interacted with e.g. it gives instructions on where a new paragraph should fall or where a coloured pull-out box should be placed, XML's symbols and tags give instruction on actual content e.g. phone numbers, addresses, and particular subject headings.

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This means that you can actually search through XML files to find the information you're after, in a similar way to searching a database - and at the same time display the information as you would in HTML.

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XML is extensible because its markup symbols and tags are unlimited and self-defining, making it a more flexible and easier to use programme - this means that designers can literally create their own tags to organise their information as they need it to be stored and presented - rather than how it looks on a page.

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This enables the information stored in XML to be shared, defined and transmitted by other users and organisations. It can also be used in conjunction with HTML on the same web page.

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Q. Is XML similar to SGML

A. Yes and no. SGML stands for Standard Generalised Markup Language - and it is a generic system for organising and tagging elements within a document - it sets out the rules for tagging information and was established in 1986 by the International Organisation for Standards. XML follows the rules of SGML but in a pared-down way, and is specifically used for information on web pages.

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Q. What are the benefits of XML

A. There are a lot of ways in which XML can be put to good use.

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(a) It can be used to store and access information in a similar way to a database - because it describes the data is contains using elements and attributes, it is easy to retrieve information and use it in other applications and allow other companies to access it.

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(b) It also works well with other web-oriented software e.g. it can communicate with other operating systems like HTML, Java Script, Corba etc.

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(c) In addition, as XML files work on different platforms it is possible to change their structure - so they can be transformed into PDF, EDI, WML, and HTML files etc. that makes them incredibly flexible.

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(d) You can also update XML files limitlessly.

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Q. So is XML a recognised markup standard internationally

A. Yes, it was established as an international standard by the World Wide Web Consortium (W3C). Its first Recommendation was published in February 1998, and allowed for each community do design languages to suit their particular needs and integrate these harmoniously into a general infrastructure based on the general principle of XML.

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Q. What is W3C and what do they do

A. W3C was set up in 1994 (in conjunction with Tim Berners-Lee, the recognised inventor of the web) at the Massachusetts Institute of Technology, Laboratory for Computer Science [MIT/LCS] in collaboration with CERN, DARPA and the European Commission - to develop common protocols that promote the evolution of the World Wide Web and ensure its interoperability.

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Since it was formed, W3C has developed more than 35 technical specifications for the infrastructure of the Internet. Its main goals are:

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(a) Universal Access: To make the Web accessible to all by promoting technologies that take into account the vast differences in culture, education, ability, material resources, and physical limitations of users on all continents;

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(b) Semantic Web: To develop a software environment that permits each user to make the best use of the resources available on the Web;

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(c) Web of Trust: To guide the Web's development with careful consideration for the novel, legal, commercial, and social issues raised by this technology.

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You can find out more about W3C and its work online at: http://www.w3.org/

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By Karen Anderson