Public interfaces for XPath expression Abstract Syntax Tree nodes. Primary external APIs for this XPath AST model.

This XPath API is a compact set of Java interfaces that allow the in-memory representation and manipulation of XPath 2.0 expressions.The main idea of this API is to manipulate XPath expressions independently of their actual underlying representation.

It was designed to fulfill the following requirements:

• Read/Write: it should be capable of querying/visiting and modifying the internal representation of XPath expressions. The expression reading is performed by using either the visitor pattern or get-like methods. Similarly, the expression writing is done through a bunch of set-like methods.
• Round-trip: it should be capable of getting string representation of expressions from its internal encoding.
  
• Application-independent: it should be suitable to be used by a variety of applications efficiently. It should provide solutions to plug in application-dependent features, like namespace/qname manager and AST generalization and specialisation (see implementation package).
  
• Lightweight: it should be compact and therefore should define a minimal set of Java interfaces in particular by factoring similar concepts. The best example is the interface OperatorExpr which allows the representation of more than ten expression types.