Internal changes

Changed ContentEmitter to check in startElement() that qname and local-name are both supplied; this checks against parser configuration errors. This change could (should?) be retrofitted to the 6.5 branch. The change also uses a stack of namecodes so that endElement() doesn't need to look up the names in the name pool. In implementing this change, I discovered that Saxon depends on the XML parser passing the QName argument to the startElement() call, something which according to the SAX2 specification is optional. However, all known parsers supply this argument, and the code changes to cope with its absence would damage performance, so I have simply documented this as a dependency on the parser.

Implemented infrastructure for data type support:

I have changed the implementation of temporary trees (result tree fragments). The FragmentValue class has disapeared. This delayed the construction of an actual tree until it the tree was actually used as a node-set: the effect was to optimize simple uses of temporary trees but at considerable cost to the more general usage which is now permitted in XSLT 2.0. Also, the introduction of tinytrees has reduced the value of this optimization. Therefore, a temporary tree is now constructed immediately as a real tree.

A side-effect of this change is that when disable-output-escaping is used while writing nodes to a tree, the instructions to switch escaping on and off are recorded in the tree in the form of the processing instructions defined by JAXP 1.1. Previously, these instructions were recorded in a form that kept the information through an xsl:copy-of instruction, but lost the information if the tree was processed in any other way. Note that the behavior of "sticky d-o-e" (that is, the effect of disabling output escaping when writing to a temporary tree) is currently an open issue in XSLT 2.0.

The indexes associated with keys are no longer referenced from each document instance, they are handled externally. This makes it easier to share the same index implementation across all the different document implementations. The indexes are now held by the KeyManager. It uses a WeakHashMap to ensure that when a document is removed from memory by the garbage collector, its indexes are removed too.

The mechanism for keeping stylesheet signatures in the namepool has been removed. It caused a creeping "memory leak" in continuously running services, and is not really needed. It was invented to allow namepools to be copied, but this facility has never been properly documented or tested. Instead, there is now a simple check that the source document and stylesheet are using the same namepool. (This change, or a simplified version of it, has also been made to 6.5.2).

The StaticContext interface has been greatly simplified, reducing duplication and making it easier to create a new implementation of this interface. This has been achieved partly by doing some work in the XPath ExpressionParser that was previously done in the StaticContext, and partly by changing those functions such as format-number() and sort() that only work in an XSLT context to check that the context is indeed XSLT before accessing the context information.

Implemented memo functions (thanks to Robert Brotherus for the suggestion). If you specify the attribute saxon:memo-function="yes" on xsl:function, Saxon will keep a cache that maps the supplied argument values to the result of the function, and if the function is called twice with the same arguments, the original result will be returned without re-evaluating the function. Don't use this option on a function that depends on the context, or on a function that creates a new temporary tree and is required to create a new instance each time. Also note that there are cases where it may be faster to re-evaluate the function than to do the lookup; this is especially true if the argument is a large node-set.