svsathya

• Apr 1st, 2007

 

The single biggest factor in deciding whether to code your programs with SAX or DOM is programmer preference. SAX and DOM are very different APIs, Where SAX models the parser, DOM models the XML document. Most programmers find the DOM approach more to their taste, at least initially. Its pull model (The client program extracts the information it wants from a document by invoking various methods on that document.) is much more familiar than SAX’s push model (The parser tells you what it reads when it reads it, whether you’re ready for that information or not.) However, SAX’s push model, unfamiliar as it is, can be much more efficient. SAX programs can be much faster than their DOM equivalents, and almost always use far less memory. In particular, SAX works extremely well when documents are streamed, and the individual parts of each document can be processed in isolation from other parts. If complicated processes can be broken down into serial filters, then SAX is hard-to-beat. SAX lends itself to assembly-line like automation where different stations perform small operations on just the parts of the document they have at hand right at that moment. By contrast, DOM is more like a factory where each worker operates only on an entire car. Every time the worker receives a new car off the line, they have to take the entire car apart to find the piece they need to work with, do their job, then put the car back together again before moving it along to the next worker. This system is not very efficient if there’s more than one station. DOM lends itself to monolithic applications where one program does everything. SAX works better when the program can be divided into small bits of independent work