Subject: Re: [xsl] Nested filters, or filter too complicated. From: "Kerry, Richard richard.kerry@xxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> Date: Wed, 17 Jan 2018 16:53:20 -0000 |
Michael, Martin, Thank you both for your replies. I knew the text() entries were not necessary but I'd left them in for clarity (*). I had missed (ie not realized) the issue about string-values, comments, etc. Martin, both of your versions gave "Ambiguous rule match". Michael, having fixed one minor error, a spurious extra ')' immediately before the final ']', I found that your version also gave "Ambiguous rule match". On giving a priority of 1 to the simpler filter and 2 to all your various suggestions I am now finding it is working and giving the result I want (ie all three options work). Was the ambiguous rule match because both are just classed as having a filter, and the rule selection doesn't care that one has a more complex filter than the other? I had sort of realized that I was doing a join, though as I have very little experience of database work I hadn't thought to use the term. I am using Saxon 9.8.0.3 so XSL 2 is fine. I think 3 would be too but I only have experience as far as 2. So thank you both, I am now able to get the results that I need. Regards, Richard. (*) clarity in the sense that although it was more verbose I thought it made my intent clearer. [Blue line] Richard Kerry BNCS Engineer, SI SOL Telco & Media Vertical Practice T: +44 (0)20 3618 2669 M: +44 (0)7812 325518 4 Triton Square, Regents Place, London NW1 3HG richard.kerry@xxxxxxxx<https://webmail.siemens-it-solutions.com/owa/redir.asp x?C=9fb20d019e3e4cb99344d708709a3177&URL=mailto%3arichard.kerry%40atos.net> [Atos logo] This e-mail and the documents attached are confidential and intended solely for the addressee; it may also be privileged. If you receive this e-mail in error, please notify the sender immediately and destroy it. As its integrity cannot be secured on the Internet, the Atos group liability cannot be triggered for the message content. Although the sender endeavours to maintain a computer virus-free network, the sender does not warrant that this transmission is virus-free and will not be liable for any damages resulting from any virus transmitted. ________________________________ From: Michael Kay mike@xxxxxxxxxxxx <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> Sent: 17 January 2018 16:29 To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx Subject: Re: [xsl] Nested filters, or filter too complicated. You're trying to do a join. That involves comparing items from two different sets. In SQL (and in mathematical predicate logic) you do this by binding "range variables" to the items in each set, and then using predicates such as where X.ref = Y.id You can use the same approach in XSLT, but with caveats. Only with XSLT 3.0 are you allowed to bind variables within an XPath expression. But that's where "." and "current() come in. Within a predicate, "." is used as an implicit range variable for the set you are filtering. You can also sometimes use "current()" as your second range variable. Or you can bind variables explicitly using xsl:variable. The problem about using ".", however, is that it changes its meaning in a nested predicate. In this case in XSLT 2.0 upwards, current() rescues you: match="type[.='Action'][$data/device-description/param[@name=current()/../bas e-name]/@standard='no')] " (Note I've avoided the use of text() here. It's much better to compare with the string-value of the element, rather than with its text nodes - it will continue to work, for example, if the text is split up by comments). XSLT 2.0 defines that current() within a pattern refers to the node being tested against the pattern. Unfortunately though (IIRC), XSLT 1.0 didn't allow use of current() in patterns. But no-one is still using XSLT 1.0, are they??? Michael Kay Saxonica On 17 Jan 2018, at 15:19, Kerry, Richard richard.kerry@xxxxxxxx<mailto:richard.kerry@xxxxxxxx> <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx<mailto:xsl-list-service@xxxxxxxxxxxx rytech.com>> wrote: I am trying to use XSLT to process one XML file, which refers to data in another, and I am having trouble with getting a filter to work. The first source file (device.xml) - the one that is actually processed by the XSL - has entries like this: <device-description> <device-value> <base-name>PollNow</base-name> <name>Poll Now</name> <type>Action</type> </device-value> <device-value> <base-name>StartupPollNow</base-name> <name>Startup Poll Now</name> <type>Action</type> </device-value> <device-value> <base-name>Ping</base-name> <name>Ping</name> <type minimum-length="0" maximum-length="256" >String</type> </device-value> </device-description> One of the templates is approximately as follows: <x:template match="type[text()='Action']" > <!-- do basic action. --> </x:template> This quite happily matches all the <device_name> elements where the <type> has a text value pf "Action". However, I have a second XML file (device-3.xml) which contains some data that I wish to use to modify the behaviour of the transform. It has entries like this: <device-description> <param name="PollNow" standard="no" > <name>Poll Now</name> <description>normal poll</description> </param> <param name="StartupPollNow" standard="no" > <name>Startup Poll Now</name> <description>startup poll</description> </param> <param name="Ping"> <name>Ping</name> <description>Ping-Pong</description> </param> </device-description> The second file is accessed via a variable, as follows: <x:variable name="data" select="document($in-file-3)"/> What I want to achieve is that for all <type> elements where there is a corresponding <param> where base-name is the same as param/@name, I want a different action. The additional template I have for this is currently as follows <x:template match="type[text()='Action'][$data/device-description/param[@name=../base-nam e/text()]/@standard='no')] " > <!-- do different action. --> </x:template> My thinking is that the first filter is as with the first template I listed, matching all <type> elements whose text is "Action". The second filter should then enable me to pick the right param from the second file, and do something based on the value of its @standard. Maybe once I'm in the second filter I am causing confusion as to which element the @name refers to (which should be the param) and which the ../base-name is relative to (the device-value/type)? Can I do all this within a single template's @match ? Or am I making it too complicated. In which case how might I get the result I'm looking for? Appreciatively, Richard. The examples are all slightly simplified from the real data, which has more elements, and the transforms are in a mode. Richard Kerry BNCS Engineer, SI SOL Telco & Media Vertical Practice T: +44 (0)20 3618 2669 M: +44 (0)7812 325518 4 Triton Square, Regents Place, London NW1 3HG richard.kerry@xxxxxxxx<https://webmail.siemens-it-solutions.com/owa/redir.asp x?C=9fb20d019e3e4cb99344d708709a3177&URL=mailto%3arichard.kerry%40atos.net> [Atos logo] This e-mail and the documents attached are confidential and intended solely for the addressee; it may also be privileged. If you receive this e-mail in error, please notify the sender immediately and destroy it. As its integrity cannot be secured on the Internet, the Atos group liability cannot be triggered for the message content. Although the sender endeavours to maintain a computer virus-free network, the sender does not warrant that this transmission is virus-free and will not be liable for any damages resulting from any virus transmitted. Atos, Atos Consulting, Worldline and Canopy The Open Cloud Company are trading names used by the Atos group. 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