Simple API For XML - XML Processing With SAX

XML Processing With SAX

A parser that implements SAX (i.e., a SAX Parser) functions as a stream parser, with an event-driven API. The user defines a number of callback methods that will be called when events occur during parsing. The SAX events include (among others):

• XML Text nodes
• XML Element Starts and Ends
• XML Processing Instructions
• XML Comments

Some events correspond to XML objects that are easily returned all at once, such as comments. However, XML elements can contain many other XML objects, and so SAX represents them as does XML itself: by one event at the beginning, and another at the end. Properly speaking, the SAX interface does not deal in elements, but in events that largely correspond to tags. SAX parsing is unidirectional; previously parsed data cannot be re-read without starting the parsing operation again.

There are many SAX-like implementations in existence. In practice, details vary, but the overall model is the same. For example, XML attributes are typically provided as extreme name and value arguments passed to element events, but can also be provided as separate events, or via a hash or similar collection of all the attributes. For another, some implementations provide "Init" and "Fin" callbacks for the very start and end of parsing; others don't. The exact names for given event types also vary slightly between implementations.