Package overview for net.sf.saxon.pull

This package provides an experimental pull API for Saxon: that is, it allows an application to read serially through a document, reading "events" such as the start and end of elements, text nodes, comments, and processing instructions, in the order in which they appear. In fact, the API allows access not just to a single document, but to any sequence consisting of nodes and atomic values: when a node is encountered, the pull API does a traversal of the subtree rooted at that node, before moving on to the next item in the sequence.

The API, defined in class `PullProvider`, is loosely modelled on the StAX `XMLReader` API. It is not identical, because it is designed as an intimate and efficient interface that integrates with Saxon concepts such as the `SequenceIterator` and the `NamePool`. A class `StaxBridge` is available that provides the `PullProvider` interface on top of a StAX pull parser; however, because pull parsing is not yet a standard feature of the Java platform, and because at the time of writing the available StAX parsers appear to be buggy, `StaxBridge` is not included in the `saxon.jar` distribution, but is instead supplied as a sample application in the `samples` directory.

The three main kinds of `PullProvider` are:

- StaxBridge, which is an interface to a pull-mode XML parser

- TreeWalker, which delivers events based on an in-memory tree. There is one general-purpose TreeWalker that can handle any Saxon tree (any tree that implements the NodeInfo interface) and aother that is optimized to the TinyTree implementation.

- VirtualTreeWalker, which delivers events representing the nodes constructed by a stylesheet or query, without actually constructing the nodes in memory. (Note that this doesn't currently work if the constructed nodes need to be schema-validated).

Some examples of application code using the pull interface with Saxon are provided in the `PullExamples.java` file in the samples directory.

Michael H. Kay
Saxonica Limited
30 March 2005