First question: in your grouping of properties using the rdf:about attribute,
are the groups adjacent? The for-each-group[@group-adjacent] instruction is
fully streamable according to the XSLT 3.0 rules, and the Saxon implementation
is also streamable (though in some circumstances -- I would need to check -- it
may build the content of each group in memory before moving on to the next).
If the groups aren't adjacent, then you can use
xsl:fork/xsl:for-each-group[@group-by], but this isn't really fully streamed
because it will typically collect all the groups in memory.
The next concern is about doing a two-pass transformation where both passes are
streamed. This hasn't really received as much attention as it should in either
the spec or in Saxon. I think it should be possible to pipe the result of the
first transformation directly into the second provided both are written as
free-standing stylesheets (as distinct from a "micro-pipeline" within a single
stylesheet). But I'm not sure I've tested this.
As to the question " how do I even begin analyzing the streamability o this
approach in XSLT 3.0?" I think the answer is suck it and see. First ask
yourself "does it seem intuitively streamable?" in the sense that the Nth thing
in the output can be computed from the Nth thing in the input, plus perhaps a
little bit of memory of earlier things in the input. If the answer to that is
yes, then try writing the code and see if Saxon complains.
Michael Kay
Saxonica
My use case is as follows -- a triplestore returns streaming RDF/XML
(omitting namespaces):
<rdf:RDF>
<rdf:Description rdf:about="http://dbpedia.org/resource/Copenhagen";>
<dct:title>Copenhagen</dct:title>
</rdf:Description>
...
<rdf:Description rdf:about="http://dbpedia.org/resource/Copenhagen";>
<dbo:country rdf:resource="http://dbpedia.org/resource/Denmark"/>
</rdf:Description>
...
</rdf:RDF>
Since it's streaming, every resource description only contains one
property. It's not convenient, so during the first pass I group the
descriptions by subject using [1]:
<rdf:RDF>
<rdf:Description rdf:about="http://dbpedia.org/resource/Copenhagen";>
<dct:title>Copenhagen</dct:title>
<dbo:country rdf:resource="http://dbpedia.org/resource/Denmark"/>
</rdf:Description>
...
</rdf:RDF>
Then as the second pass I do the main transformation to XHTML, which
could produce something like using [2][3]
<fieldset>
<label>Title</title>
<input type="text" value="Copenhagen"/>
<label>Country</title>
<input type="text" value="http://dbpedia.org/resource/Denmark"/>
...
</fieldset>
where fieldsets represent resources, and labels/inputs represent
properties/values.
Now my question is, how do I even begin analyzing the streamability of
this approach in XSLT 3.0? I guess my main concern is that such
grouping would not be streamable, but maybe there are other solutions?
Thanks.
Martynas
[1]
https://github.com/AtomGraph/Web-Client/blob/master/src/main/webapp/static/com/atomgraph/client/xsl/group-sort-triples.xsl
[2]
https://github.com/AtomGraph/Web-Client/blob/master/src/main/webapp/static/com/atomgraph/client/xsl/bootstrap/2.3.2/layout.xsl
[3]
https://github.com/AtomGraph/Web-Client/blob/master/src/main/webapp/static/com/atomgraph/client/xsl/bootstrap/2.3.2/imports/default.xsl
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