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The semantic web

XML (eXtensible Mark-up Language) is the future language of the Web. Developed from SGML, XML is used to create high-structured and formatted documents for the Web. And has been specifically developed by the World Wide Web Consortium (W3C) to overcome the inherent limitations posed by HTML.

Those familiar with HTML may have an idea about the 'mark-up' technique. In HTML, elements are used to 'mark-up' the text i.e. to include clues in the text to make the browser display the matter in a specified form. Tags(open and closed)/meta data are embedded in the text to provide clues to the browser. Simply put, 'marking-up' is specifying the enhancements or structuring of text in a document. It includes the document format, font style and size, and appearance with respect to alignment etc.

The reason why HTML and XML documents look similar is because they have a common parent- SGML. The basic difference however, is that HTML has predefined tags and attributes. XML conversely, lets you create new tag languages. These languages can then be used to create tags that are tailored to your content needs. These tags can contain attributes used to explain the data as well. This provides immense flexibility thus making it 'extensible'. In addition, hyper linking in XML is more powerful, and the browser view more effective.

To view XML documents, one needs a XML browser. However, there is no such browser that supports all the features of XML. Netscape 6, Mozilla and Opera provide high XML support.

But before we go any further a quick guide to the XML alphabet soup. First there are XML Accessories which are languages created using XML that exploit its capacities. Examples of these are XML Schema, XML Names, XPath, XLink, XML Base, and XPointer. Then there are XML Applications which are languages that define the constraints of XML data in a class. Common examples are MathML and SMIL. Finally, there are XML Transducers such as CSS2, XSL and XSLT used to convert XML input into a particular output.

The XML protocol was developed to power web services and increase interoperability, and as a contender to Microsoft SOAP protocol. Both protocols allow the free flow of information between systems, applications and technologies. Yet ironically, XML has been heavily adopted by Microsoft.

There has been a remarkable shift from the importance given to 'components,' to the use of web services. These web services will be facilitated by XML and are components that can be accessed via the net. They increase e-business efficiency by overcoming constraints of the component model. Most importantly, web services are dynamic and can be invoked on the fly. This allows faster and cheaper integration to provide useful and viable products, which can reduce development time from a few months to a matter of days. However, there are some bottlenecks like inadequate security, standards, quality of service and the threat from competition that need to be straightened out.

Tim Berners Lee prediction of the emergence of the Semantic Web is being brought about through XML. Efforts to create this Web are already underway as W3C has already given the green signal for it. Programs that would facilitate the collection of content from diverse sources on the web will be created. This information will then be formatted, adapted or exchanged with the help of other programs.

When information needs to be accessed by different systems on the same network, it has to be in a format that can be understood across the systems. It also makes sense to have the information stored in a form that can be accessed and reused whenever necessary. This can cut-down on cost and save up on resources, and XML seems to be the answer. Today many other technologies are making room in order to accommodate XML, thereby increasing its scope.

Some of the practical applications of XML include simplifying the process of web publishing. New XML technologies have thus helped build huge corporate databases and complex, dynamic web sites. XML is also finding its way into configuration, distributed computing, storage, directory services, and knowledge management.

IBM, Microsoft and Sun are contenders in the XML space, while other smaller players are trying to ally themselves with one of them. IBM's WebSphere application server has Linux and Apache, J2EE and XML as core components. Sun has come up with XML processing packages like JAXP and JAXM. Microsoft's .NET bundled with SOAP (Simple Object Access Protocol) joins the fray in its attempt to rule the XML world.

Archana Jayakar
[email protected]

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