Why XML ?

In order to appreciate XML, it is important to understand why it was created. XML was created so that richly structured documents could be used over the web. The only viable alternatives, HTML and SGML, are not practical for this purpose. HTML has been developed for something else and is not suited for data exchange and storage of structured data.

HTML, as we’ve already discussed, comes bound with a set of semantics and does not provide arbitrary structure. To do something with HTML you have to use fixed set of tags provided by the language.

SGML provides arbitrary structure, but is too difficult to implement just for a web browser. Full SGMLsystems solve large, complex problems that justify their expense. Viewing structured documents sent over the web rarely carries such justification.

This is not to say that XML can be expected to completely replace SGML. While XML is being designed to deliver structured content over the web, some of the very features it lacks to make this practical, make SGML a more satisfactory solution for the creation and long-time storage of complex documents. In many organizations, filtering SGML to XML will be the standard procedure for web delivery.

XML, or eXtensible Markup Language, is a meta-language, a language used to define and create other languages. XML provides rules for describing the structure of a document, thus facilitating the exchange and publication of information.

XML has the following features:

• Extensibility

The author may define tags and how they are to be processed. It is extensible because author can extend its functionality by adding new tags.

• Document structuring:

Unlike HTML, XML describes the structure of the document.

• Validation:

The document can be checked to ensure that it conforms to the required syntax and that it contains all of the required parts.

• Convertibility:

XML provides a basic data format that can be output to different devices, attached to different stylesheets to enable a range of presentation styles, and delivered in whole or in pieces.

• Flexibility

XML is a very flexible language and yet easy to learn and use, unlike SGML, its originator which was not so flexible. What one, need is just remember the basic XML guidelines and don’t forget that there is on other rule in XML.

Advantages of XML

• Separates structure from presentation

As a result, it is much easier to manipulate XML and put it to various uses.

• Flexibility and extensibility

XML enables users to create their domain-specific markup languages. XML can accomodate a wide range of communities, from musicians to chemists to students.

• Sustainability

XML is self-describing; humans can, in general, discern the meaning of XML tags, and there’s a lot of clear XML documentation to help this process. Whereas proprietary data formats are difficult to preserve, XML can be created in ASCII, which is stable and likely to be readable for a long time.

• Exchange of data

XML can easily be transformed according to the user’s needs. For instance, businesses can receive data from another company’s system and translate it for their own. XML is non-proprietary, hardware- and software-independent, and fairly simple to author, so it is a natural choice for the exchange of information among different applications. Moreover,

• Enables more powerful, targeted searches, allowing you to search within different categories of data, or fields. With the HTML document, search software wouldn’t be able to distinguish an author’s name from anything else, but XML defines specific categories and structures. For instance, if you are looking for “Rice” the street name rather than the grain or the university, you might search within a specific address field.

• Enables reuse and provides different views of the data to different users

Because XML defines the structure of the document and the relationship among parts, it can be used for many different purposes. “A single data source can be used in different ways for different media.  If you need pull out and present a subset of information from an XML file (say, for instance, a list of classes offered at a particular time), XML enables that selective presentation. Since the source has a clear structure, the conversion can be automated. Links, for example, can be emphasized in the print only in the format (e.g. italic) whereas they could be hyperlinks on a CD-ROM. Thus, independence from hard- and software is ensured: if, for example, the software used for printing changes, the conversion of this output format is adapted and the data source remains unchanged

XML in Future Web Development

XML is going to be everywhere

We have been participating in XML development since its creation. It has been amazing to see how quickly the XML standard has been developed and how quickly a large number of software vendors have adopted the standard.

We strongly believe that XML will be as important to the future of the Web as HTML has been to the foundation of the Web and that XML will be the most common tool for all data manipulation and data transmission.