XML and XSLT Transformations

Known more formally as eXtensible Markup Language, XML is a generalized markup language useful for structuring many kinds of documents. XML encodes semantic information about a document's structure in tags similar to those used in HTML. Thus XML can be easily read by a number of software applications and has become a standard data format. However, XML does not record information about how a document should be presented or displayed; that is left to the application reading the document. XML documents can also be transformed readily to other formats. The eXtensible Style sheet Language Transformations(XSLT) allow users to present XML documents in any format. XSLT transformations are written in the eXtensible Style sheet Language which encodes the rules of presentation allowing an XML document to become an HTML web page, plain text file, or anything else. For instance, users of this dictionary may want to turn dictionary entries into web pages as part of an online system. Transformation into an html file is not the only option, of course. Using XSLT, the dictionary may also be transformed, for instance, into a SQL batch file suitable for loading into a database. Skilled programmers can even use XSLT to transform the dictionary into PDF or MS Word Format using XSL Formatting Objects(XSL-FO). This is accomplished using a processor such as the Apache Project's FO processor.

The transformation requires three components: An XML file, XML Style sheet and a processor capable of executing the transformation. The Style sheet contains the rules for presentation. Information about making style sheets can be readily found on the world wide web. This tutorial, reference and example page are all good places to start, but there are many more in addition as well as numerous books. There are several commonly used XSLT processors including Saxon and Xalan. These processors generally work on the command line. In addition, many graphical XML editors will perform XSLT transformations. Oxygen is a powerful visual editor with extensive support for XSLT. Meanwhile, the Xray editor is free and also supports XSLT well.

Included in this release is an example transformation that will convert the tamil_dictionary.xml file into a simple html document. This transformation will generate a single, very large, html web page that presents each dictionary entry in a table. This example should demonstrate all the elements of a transformation and provide XML novices with a starting point for their own transformations.

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