Subject: Re: [xsl] General rule for designing XPath expressions to return items in document order? From: Andrew Welch <andrew.j.welch@xxxxxxxxx> Date: Fri, 10 Jan 2014 11:01:23 +0000 |
On 10 January 2014 10:56, Costello, Roger L. <costello@xxxxxxxxx> wrote: > David wrote: > > I haven't checked the streaming rules in detail > but I would expect //head to be streamable. > (You might not be able to access any of the > child nodes in a streamable way but for example > count(//head) ought to be able to count all the > head in the document in a single pass. > > Michael responded: > > That's a fair summary. //head is "consuming" > (it reads the input stream), and "crawling" > (it accesses all the nodes in the subtree). When > you get an expression that is consuming and > crawling, you are allowed to do "inspection" > operations on the result, for example count() > > But Michael doesn't that contradict section 19.1 of the XSLT 3.0 specification: > > For example <xsl:value-of select="//head"/> will > still fail the streamability tests, because of the > possibility that one head element is a child of > another. This problem can be remedied by > writing <xsl:value-of select="//head/text()"/>. He did also say: "but you are not allowed to do "absorption" operations such as string() or data() or copy-of()." and you quote from the spec is effectively that. -- Andrew Welch http://andrewjwelch.com
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