The Book of SAX

Essentially, XML is for describing the structure of a document, and a document can be any information in written form - from a complete customer billing history to a restaurant menu. XML is already used in many areas of business, and it will become increasingly important as it supersedes HTML. But why do we need to describe the document's structure?


Well it's not so much for us, but for computers so that they can process the information contained in the document. We can easily see the structure by reading it, but a machine must be able to follow such instructions as 'Take the customer billing history and show me all completed transactions for January of this year.' The machine does this by reading what are known as 'tags' such as

<transaction status="complete">
  <date>02/01/2002</date>
  <amount>504.45</amount>
</transaction>

This process is known as 'parsing'. There are two methods of parsing XML. The first uses what is known as the Document Object Model (DOM), which is similar to the way a chemist will examine the structure of a molecule by building a 3D model of it. The second uses SAX, the Simple API for XML. Using the SAX method is like waiting for your baggage at a single-circuit carousel at an airport. Various items go past and you take off the items you're interested in.

Parsing is what this book is all about. It's a practical guide for programmers working in Java and Visual Basic. The book falls into two sections. The first is a series of chapters which explain the fundamentals of the SAX API with reference to code examples that are downloadable from the book's website. The second part covers the SAX 1.0 and 2.0 API documentation, illustrated with short code examples in the text.

The emphasis is on practicality, and anyone whose task it is to manipulate XML programmatically can count on a flannel-free guide to how it's done. Seasoned Java programmers might be a little irritated by the code style - the authors clearly have a C/C++ background - but it's clear and reassuring that they are thoughtful programmers who are concerned with clarity, accuracy and efficiency.