Using an XML Processor

Applications access XML data through an XML processor, a software library for reading, modifying, and writing XML data.

An XML processor enables applications to read (“parse”) XML data and checks that the data are “well-formed” according to the basic rules of XML (e.g., every start tag has a corresponding end tag). Parsing can optionally validate XML data against application-specific rules from a developer-supplied Document Type Definition (DTD) or XML schema. During parsing, the application can get pieces of the data through the Simple API for XML (SAX).

After parsing, the processor can store the data in an XML document object in memory. The application can examine and change document objects through the XML Document Object Model (XML DOM) API.

Processors can also transform one document object into another, using a developer-supplied script in the XML Stylesheet Language Transformations (XSLT) language. For example, an XSLT script might transform an XML purchase order in one company’s format into the format used by one of its business partners. Such transformations usually take less code in XSLT than they would in conventional programming languages. Also, putting transformations in XSLT script keeps them separate from the application code, which can make them easier to change when the application’s XML data formats change. Applications can also search XML document objects using XPath, a standard query language that’s part of XSLT.