[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: XQuery -- Reinventing the Wheel?
Michael Rys wrote: > Evan, you actually left out an important result of your > simplistic formula, > by elminiating the template rules and stratifying some of the semantics, > XQuery aims to become better optimizable for people that care about > performance and scalability. It also will become strongly typed if complex > and simple type is available, which XSLT 2.0 will not be. I fully recognize this is the reason why rules and the ancestor axis, etc. are not a part of the XQuery language. This, however, does not address my point. If it's basically true that XQuery = XSLT - templateRules - nonAbbreviatedXPathAxes %datatypes as you seem to acknowledge, then it should be defined that way! If a subset of XPath or XSLT is necessary in order for query implementations to work, that's fine; define the subset. The Quilt/XQuery authors clearly put a great deal of work into defining the query constructs, words, syntax, etc. of XQuery. With all due respect, that work has already been done in a rather large subset of XSLT, again modulo datatypes. Again, my point is that the transformation language and the query language, if they are not the same thing, should build from a common semantic and syntactic base. Section 2.11 of the XSLT 2.0 Requirements WD states that XSLT 2.0 "Could Improve Efficiency of Transformations on Large Documents," specifically addressing the possibility of defining a subset of XPath "that does not require random access to the source tree." This would basically be XQL/XQuery's path language (without perhaps the requirement that expressions be abbreviated). I just discovered this section, and I think *it* should be the germ of the W3C XML Query Language, fully informed by the work of the XML Query WG on the query algebra. I feel quite strongly that there is a better way than to define an entirely new syntax and semantics, when so much of what is needed is already found in XSLT or is slated for a future version of XSLT. This passage right here should be the germ of the XML Query Language syntax. I hope that what comes out of it will make the XQuery Working Draft obsolete, for the good of the people who would benefit from the reuse of W3C technology where reuse is absolutely appropriate. <quote href="http://www.w3.org/TR/2001/WD-xslt20req-20010214"> 2.11 Could Improve Efficiency of Transformations on Large Documents Many useful transformations take place on large documents consisting of thousands of repeating "sub-documents". Today transformations over these documents are impractical due to the need to have the entire source tree in memory. Enabling "progressive" transformations, where the processor is able to produce progressively more output as more input is received, is tantamount to avoiding the need for XSLT processors to have random access to the entire source document. This might be accomplished by: * Identifying a core subset of XPath that does not require random access to the source tree, or * Consider a "transform all subtrees" mode where the stylesheet says, "Apply the transformation implied by this stylesheet to each node that matches XXX, considered as the root of a separate tree, and copy all the results of these mini-transformations as separate subtrees on to the final result tree." </quote> Evan Lenz XYZFind Corp.
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