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Thank you Mike for an enlightening description. I'll study the source code of Saxon as I get time. Presently I am happy using Saxon! Its very nice. Regards, Mukul --- Michael Kay <mike@s...> wrote: > > I start an unrelated topic. How do you implement > > xsl:template name="something" and its required > > instruction xsl:call-template in the XSLT > processor. > > i.e. what kind of data structures do you use in > Java > > and what kind of control flow takes place. Am just > > curious since many days.. > > Depends greatly on the processor. Saxon compiles > each template or function > into an abstract syntax tree, which is then heavily > re-arranged by the > optimizer and type-checker, and is then executed > interpretively at run-time. > A call-template instruction is a node in this tree, > containing a pointer to > the tree representing the template to be called. > Template names aren't used > at run-time, they are fully resolved at compile > time. > > You asked about control flow. In Saxon 6.x, and > probably in most XSLT 1.0 > processors, the XSLT and XPath engines were very > separate. In 8.x they have > become much more integrated, probably reflecting the > influence of XQuery. > However Saxon still has two modes of execution > internally, pull and push: > expressions such as path expressions are usually > evaluated by a stack of > iterators [expletive deleted] data in a pipeline from the source > document, while element > and attribute construction instructions are usually > evaluated by means of a > push pipeline pushing SAX-like events out to the > serializer (or the result > tree builder if the user requests one). Control > instructions such as xsl:if > and xsl:call-template can be evaluated in either > mode, depending on where > they appear. There's also a fairly experimental > capability to execute > element constructors in pull mode, leading to lazy > tree construction, so > parts of a temporary tree that aren't ever > referenced don't actually get > built. > > If you're interested in understanding such things it > would be instructive to > read the source code of a processor such as Saxon. > It's probably a bit > daunting at first, but you'll find it interesting. > > Michael Kay > http://www.saxonica.com/ > > > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
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