Better way to structure XQuery

[David A. Lee]

A scripting language like xproc or xmlsh can do this where xquery cannot 
directly.
For example, in xmlsh


xread doc < file.xml
xpaths=(xpath1 xpath2 xpath3 xpath4)
for $x in $xpaths ; do
   r=$<(xquery -q $x -i $doc)
   xecho <[  <result>{$r}</result> ]>
done







David A. Lee
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G. Ken Holman wrote:
> At 2009-07-08 11:08 -0500, http://x-query.com/mailman/listinfo/talk wrote:
>> I have the following XQuery:
>>
>> xquery version="1.0";
>>
>> let $mydoc :=doc('http://localhost:8080/exist/rest/db/bio.xml')
>> let $profileType := 'Standard'
>> let $profileType := if
>> ($mydoc/metadata/idinfo/spdom/bounding/boundalt/altmin or
>> $mydoc/metadata/idinfo/spdom/bounding/boundalt/altmax) then 'Biological'
>> else $profileType
>>
>> return
>>    <result>
>>       {$profileType>
>>    </result>
>
> As an aside, I would have written that as:
>
> xquery version="1.0";
> <result>
>  { if ( doc('http://localhost:8080/exist/rest/db/bio.xml')/
>         metadata/idinfo/spdom/bounding/boundalt/altmin or
>         doc('http://localhost:8080/exist/rest/db/bio.xml')/
>         metadata/idinfo/spdom/bounding/boundalt/altax )
>       then 'Biological" else 'Standard' }
> </result>
>
> ... because I would assume that the processor would have cached the 
> document in memory during the transformation rather than accessing the 
> resource each time.  I'm unsure why you would have used and re-used 
> the $profileType variable.
>
>> This works fine, however, I would like to take the paths and place them
>> in a sequence (there are potentially 30+ I need to check for). I am new
>> to XQuery/XPath and unable to figure out the proper way to do this.
>>
>> Can anyone let me know how to use two variables, one being the $mydoc
>> and one being a string ($path :=
>> '/metadata/idinfo/spdom/bounding/boundalt/altmin') and have it evaluate
>> as XPath instead of as a string?
>
> There is no equivalent to eval() available to you.
>
> However, if you have a text serialization available in your XQuery 
> implementation then XQuery is composable (XSLT moreso I find because 
> it is all simple XML) so you can run two steps, the first to compose 
> the necessary XQuery that is run in the second.
>
> I have an example below that uses Saxon.  I have no idea what you want 
> to do with your XPath expressions since you are asking about getting 
> them one at a time, yet you are using two of them in your sample.
>
> I hope this helps give you an idea.
>
> . . . . . . . . . . . . . Ken
>
> p.s. I hope on Friday to announce a hands-on XQuery class in 
> California this summer ... plans are in the works and there is a 
> survey out to help determine interest in particular delivery dates
>
> T:\ftemp>type stacy.xml
> <xpaths>
> <xpath>/metadata/idinfo/spdom/bounding/boundalt/altmin</xpath>
> <xpath>/metadata/idinfo/spdom/bounding/boundalt/altmax</xpath>
> </xpaths>
>
> T:\ftemp>type stacy.xq
> declare namespace saxon = "http://saxon.sf.net/";
> declare option saxon:output "method=text";
>
> "let $mydoc := doc( 'bio.xml' )
>     return &lt;result>
> ",
> for $each in xpaths/xpath
>     return concat("&lt;subresult>
>              {if ($mydoc",$each,") then 'Biological' else 'Standard'}
> &lt;/subresult>"),
> "&lt;/result>"
>
> T:\ftemp>xquery stacy.xml stacy.xq generated.xq
>
> T:\ftemp>type generated.xq
> let $mydoc := doc( 'bio.xml' )
>     return <result>
>  <subresult>
>              {if 
> ($mydoc/metadata/idinfo/spdom/bounding/boundalt/altmin) then 'B
> iological' else 'Standard'}
> </subresult> <subresult>
>              {if 
> ($mydoc/metadata/idinfo/spdom/bounding/boundalt/altmax) then 'B
> iological' else 'Standard'}
> </subresult> </result>
> T:\ftemp>xquery bio.xml generated.xq
> Source document ignored - query does not access the context item
> <?xml version="1.0" encoding="UTF-8"?>
> <result>
>    <subresult>Standard</subresult>
>    <subresult>Standard</subresult>
> </result>
> T:\ftemp>
>
>
>
> -- 
> Possible July/August XSLT/XQuery/XSL-FO training in Oakland/CA/USA
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> G. Ken Holman                 mailto:http://x-query.com/mailman/listinfo/talk
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>
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