Parsing XML Documents
To process the data contained in XML documents, you need to write a application program (in a programming language such as Java, JavaScript). The program makes use of an XML parser to tokenize and retrieve the data/objects in the XML documents. An XML parser is the software that sits between the application and the XML documents to shield the application developer from the intricacies of the XML syntax. The parser reads a raw XML document, ensures that is well-formed, and may validate the document against a DTD or schema.
There are two standard APIs for parsing XML documents:
- SAX (Simple API for XML)
- DOM (Document Object Model)
SAX is an event-driven API. The SAX API defines a number of callback methods, which will be called when events occur during parsing. The SAX parser reads an XML document and generate events as it finds elements, attributes, or data in the document. There are events for document start, document end, element start-tags, element end-tags, attributes, text context, entities, processing instructions, comments and others.
DOM is an object-oriented API. The DOM parser explicitly builds an object model, in the form of a tree structure, to represent an XML document. Your application can then manipulate the nodes in the tree. DOM is a platform- and language-independent interface for processing XML documents. The DOM API defines the mechanism for querying, traversing and manipulating the object model built.
The JAXP (Java APIs for XML Processing) provides a common interface for creating, parsing and manipulating XML documents using the standard SAX, DOM and XSLTs.
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