SAX, the Simple API for XML

Today there are two widely accepted APIs for working with XML: the Simple API for XML (SAX) and the Document Object Model (DOM). Both APIs define a set of abstract programmatic interfaces that model the XML Information Set (Infoset). The DOM models the Infoset through a hierarchy of generic nodes that support well-defined interfaces. Due to the DOM's tree-based model, most implementations demand that the entire XML document be contained in memory while processing. SAX, on the other hand, models the Infoset through a linear sequence of well-known method calls. Because SAX doesn't demand resources for an in-memory representation of the document, it's a lightweight alternative to the DOM.

http://msdn.microsoft.com/msdnmag/issues/1100/xml/