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> In case of Saxon, would you say that there is some > intermediate representation? I think, the user (or, > programmer) has the view that he/she is just running a XSLT > program in one pass. If you look at the various APIs - including the JAXP API, it's clear that there is one operation that creates a Templates object, and another operation that uses the Templates object (repeatedly, and in multiple threads, if you wish) to do a transformation. The Templates object is the "compiled" stylesheet. In Saxon this is a heavily optimized expression tree rather than a sequence of instructions, but it's conceptually the same. (Saxon-SA in the case of XQuery also allows you to generate Java code from the expression tree, in which case the compiled representation of the query is a Java program.) > > I might guess, that prior to creation of the result XDM tree > it's compilation. Does XSLT 2.0 spec define compilation and > runtime phases for XSLT? > Not in so many words, but the distinction is there in the way error handling is specified, in the distinction between the static and dynamic context, and in facilities like use-when. The XPath 2.0 spec includes a processing model that makes a more explicit distinction. It refers to the two phases as "static analysis" and "dynamic evaluation". The term "compile" is deliberately avoided as it could be taken to prejudge implementation strategies. The output of the analysis phase is called an "operation tree", but there's nothing that says it needs to really be a tree. Michael Kay http://www.saxonica.com/
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