Internal changes

The various bit-valued static properties of an XPath expression (dependencies, cardinality, and other special properties) have now been brought together into a single word, whose value is computed once and stored on each node in the expression tree rather than being calculated on demand. (There were some cases where this calculation was still being done at run-time).

Some changes have been made to the design of tail-call optimization. This is mainly to fix a bug arising when apply-templates uses a select expression with context dependencies. The decision that a call is a tail call is now made statically rather than dynamically, to avoid the costs of creating a closure for the select expression when this is not needed.

In some cases XSLT stylesheet functions are now compiled to the UserFunction object originally introduced to support XQuery. This is done where the body of the function is sufficiently simple: this basically means that it must consist of a sequence of xsl:param elements, then xsl:variable elements, and finally an xsl:sequence element with a select attribute to define the result of the function. The effect is that recursive calls in such functions now benefit from tail call optimization, allowing deeply-nested recursive functions to execute without blowing the stack.

A small but useful speed-up has been achieved for the common operation of navigating the child axis, by optimizing for the case where all nodes on the axis are retrieved.

The XMLChar module from Xerces has been incorporated into Saxon, and is now used in most places where XML names and XML characters are tested for validity. This performs a considerably more accurate check than Saxon was previously performing, especially for characters that are valid within names.