Subject: Re: [xsl] [xslt performance for big xml files] From: Robert Koberg <rob@xxxxxxxxxx> Date: Sun, 26 Apr 2009 06:54:09 -0400 |
On Sat, Apr 25, 2009 at 07:16:04PM -0400, Robert Koberg wrote:Of all the real world applications deployed that use XQuery (I suppose
I could be more specific and say as recommended by Liam, but maybe
probably not necessary), how many do you think would work on more than
one XQuery processor?
I think quite a few, although yes, you generally will have to change the collection() and document() arguments. Try creating a SQL database and querying it in Oracle, DB2, MySQL, PostgresQL and you'll generally find you have to change the code at least a little, but that does not make SQL completely non-interoperable. It's a case of managing expectations, and of "the application was ported in a week" vs "we would need to rewrite millions of lines of code from scratch".
[...] XQuery as used/promoted by the XML DBs tend to favor their own extensions in documentation and lists (though there seems to be more caveats on the lists lately, though).
I don't actually remember which implementations I suggested -- most likely MarkLogic, Qizx and dbxml, since I've used them. I've not had major problems moving queries between them, though, once the files are indexed, which is a separate (although not unfair) question.
We didn't standardise collection() -- at some point you have to say, "this is the scope of our spec" and stop. Maybe for XQuery 1.1 we could consider an optional directory-of-files-as-collection() function, but then people would say they needed options to say whether to re-run indexes, what collation sequences and file encodings to assume, whether to follow shortcuts and sumbolic links... and pretty soon it'd be a huge mess. or at least that's been a difficulty in the past. Relational database schemas aren't entirely portable either, and neither are filenames (e.g. between MS Windows and Solaris and OS X the character sets, lengths, and default encodings differ).
You're right that extension functions are a problem -- that's true for XSLT as well, of course, and XPath, and for that matter C and Perl and Python....
best, -Rob
Liam
-- Liam Quin, W3C XML Activity Lead, http://www.w3.org/People/Quin/ http://www.holoweb.net/~liam/ * http://www.fromoldbooks.org/
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