Xml Origins and definition
The Extensible Markup Language (XML) is a metalanguage that permits to create personalized document structures.
Extensible what? Metalanguage what? Personalized what?
- Extensible:
Usual HTML pages have a strong limitation. The HTML language was created in order to furnish simple text pages and not a big number of pictures. In a world where multimedia is becoming more and more important, HTML had to reshape itself to permit the use of multimedia material inside its pages. Companies working with HTML like Microsoft or Mozilla, have implemented their HTML software with plug-ins quite often not compatible between them self. XML treat the workload in a complete different manner, by giving the possibility to extend the table that contains information on how to render the variety of different document formats found on nowadays web pages. Should another technology come out tomorrow, and they always do, HTML will need a plug-in to serve the new typology of content, while XML will only need informations on how to render the new document types. HTML is a closed language, opposed to XML that is “Extensible”. - Metalanguage:
Computers are not intelligent like humans and therefore do not get the gist of an idea as a person would. Computers follow programs which are sets of instructions in a clear and simple language. So if we order a computer to output an HTML page, it will output the text without knowing any information of what the text is about. A metalanguage is a language used to make statements about other languages. With XML we will make the computer acknowledged of the structural meaning of a paragraph of text. This knowledge will make the computer able to process more advanced tasks rather then just display text. These tasks could comprehend sorting of data, automatic relationships between documents related to the same arguments, and simple transportation of information between different websites. - Personalized document structures:
If the browser knows that a bit of text of a document represents the title of the document itself, or perhaps the name of the product that a company is trying to promote through a web page, it is very easy to understand that XML opens the doors to a variety of representations of the same single document. You may want to exclude some parts of the document on the version of the page that will be visualized by mobile phones. Simple. Because XML is organized with a tree structure, is only matter of recalling only those beats (technically called nodes) that are needed by the described document representation.
These are a couples of the peculiarity that make XML a very powerful and yet at the same time clear language. But what are the origins of XML? Since how long does it exists?
XML was born by the need to bring to the World Wide Web the Standard Generalized Markup Language (SGML), the international standard used to give meaning to the structure and the content of electronic documentation of any kind.
XML was developed by the XML Working Group (originally named as SGML Editorial Review Board) constituted under the willing of the World Wide Web Consortium (W3C) on 1996. President of the work group was Jon Bosak from Sun MicroSystems with the active partecipation of the XML Special Interest Group (known previously as SGML Working Group).
It contains all the power of SGML, but it does not contain all the particular functions that are not used generically. The main characteristic of XML is the simpleness by which is possible to write, share and transmit documents on the Web.
Goal of this group was to bring SGML on the web. The planning of the development of the XML Language was completed by examining pros and cons of the SGML language. XML was firstly presented to the public when SGML celebrated its tenth year of life.