Cart
[Home] [By Thread] [By Date] [Recent Entries]
> > how much is the current xquery draft http://www.w3.org/TR/xquery-11/ > > tracking http://www.w3.org/TR/xqueryx/ I'm not sure what the verb "to track" means. I thought it meant something like "to follow". The answer to that is that the XQueryX syntax follows the XQuery syntax, not the other way around. In terms of moving it forwards to 1.1, we do occasionally have problems that the evolution of syntax in XQuery leads to XQueryX changes that are not backwards compatible with XQueryX 1.0 - I think we've managed around that problem, but I don't follow XQueryX that closely. > > Were there arguments ever to model the grammer with xml then > derive a shorthand version of XQuery e.g. you have mentioned > the benefits but what are the limitations ? The problems with evolution of the XQuery grammar relate largely to the problem that arbitrary "bare names" can be used as expressions, but they can also be used as keywords, and the two uses of a name (or other symbol such as *, /, or .) are distinguished by context. XSLT avoids that problem because there are clearly different syntactic contexts - element names, attribute names, attribute values - distinguished by the XML parser before XSLT or XPath processing even starts. > > Also we saw some extensions at XML Prague of xquery > (presented by Matthias Brantner) > http://www.xmlprague.cz/2010/sessions.html#Extending-XQuery-with-Collections -Indexes-and-Integrity-Constraints > > I found this to be rare demonstration of how XQuery can be > extended with a minimum of fuss and wondered if you had any > opinions on this as well. They've done two kinds of extension, as far as I can see: (a) new functions, which is unproblematic (b) new declarations in the prolog. The rule for a new prolog declaration to be unambiguous is that it must start with two keywords (for example "declare integrity") where the second keyword does not clash with a word that can appear in an operator context (such as "and", "then", "as", "with" - the list is quite long and growing because of Update and Free Text). They have taken a gamble that the words "collection", "integrity", "value", "ordered" will never be used in an operator context in a future version of the standard. In XSLT, the second kind of extension can be done without breaking conformance and interoperability by using a top-level element (such as <m28:declare-collection>) in a vendor namespace. Your stylesheet will then continue to run with products that don't recognize this extension. With XQuery extensions like these, your query becomes completely non-interoperable if you use the vendor extension. (Generally, the XQuery user community, perhaps because it grew out of the SQL user community, is far more tolerant of non-interoperability than the XSLT user community, whose expectations are set more by HTML: if you conform to the spec, you should get identical results in every browser, and if you don't, you still get a reasonable approximation in every browser.) Regards, Michael Kay http://www.saxonica.com/ http://twitter.com/michaelhkay
[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] |
