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Alan Gutierrez wrote:
>* Jeff Rafter <email@example.com> [2004-12-27 14:40]:
>>>> Say the test was /foo/bar/[baz2="test"]/baz1
>>>> If your schema stated that the children were (baz1,baz2,baz3)
>>>> wouldn't you have enough information to know to surrender when
>>>> you reached baz3?
>>Unfortunately that solution doesn't win much against the DOM or other
>>tree based models.
> It does if your predicate can fail early.
>>For example if your schema asserted (as you say) that the content
>>model of bar be (baz1, baz2, baz3) and that baz2="test" always--
>>then you could "surrender" at the point of baz1 by starting with
>>the assumption of validity. If the document turns out to not be
>>valid you could raise some special error that says essentially--
>>hey we assumed this was valid and it isn't so we don't know if we
>>reported the right thing or not.
> Or, to simply the implementation, a valid document could be a
> requirement, which is what I was imagining.
Ah. The pipelining approach. Perfectly sensible. Luckily most schema
languages support validation via streaming API (Schematron is a bit of a
problem, unless its query sublanguages are themselves restricted to our
XPattern), so we don't run into the awkward problem that we have to tree
up a document earlier in the pipeline for validation.
But I'd say for a first pass at XPattern we leave out Schema aids and
maybe they could be a subject of a later "level", as long as one could
work in ecumenical schema language support.
Uche Ogbuji Fourthought, Inc.
http://uche.ogbuji.net http://4Suite.org http://fourthought.com
Use CSS to display XML - http://www.ibm.com/developerworks/edu/x-dw-x-xmlcss-i.html
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Be humble, not imperial (in design) - http://www.adtmag.com/article.asp?id=10286
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A survey of XML standards - http://www-106.ibm.com/developerworks/xml/library/x-stand4/
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