How to refer to XML data not in the iterated objects?

[rorlic]

If I have a XML like the following and I am iterating over /cartoons/cartoon, how do I refer to an attribute (e.g. /cartoons/@source) or element (e.g. /cartoons/updated) using rml:reference or rr:template?

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<cartoons source="Disney Inc.">
    <updated>2019-12-05T09:26:49Z</updated>
    <cartoon id="1">
        <name>Mickey Mouse</name>
    </cartoon>
    <cartoon id="2">
        <name>Donald Duck</name>
    </cartoon>
</cartoons>

I tried using the following without success (using carml):

• rml:reference "../updated"
• rml:reference "/cartoons/updated"
• rr:template "{../updated}"
• rr:template "{/cartoons/updated}"

Update
also tried:

• rml:reference "parent::*/updated"
• rr:template "{parent::*/updated}"

[bjdmeest]

Hmmm, it might be that carml doesn't support xpath parent expressions, bc this works (rml:reference "../updated") for the RMLMapper-JAVA. However, that sounds weird as carml is using the same xpath library. Could you share the complete mapping?

[pmaria]

CARML does not resolve XPath parent expressions outside the iterated items due to its streaming nature. Basically, each logical source produces a stream of sub documents which are not connected to the full DOM of the underlying source. This is one of the few downsides of the streaming approach.
I'm hopeful that we can add language features to RML which would allow to solve this in a general way, such that this can be used for other reference formulations as well.

[rorlic]

Based on the above and a little experimenting I have found a workaround: I simply add the following to the mapping above.

:CollectionMap a rr:TriplesMap;
  rml:logicalSource [
    rml:source "cartoons.xml";
    rml:referenceFormulation ql:XPath;
    rml:iterator "/cartoons";
  ]; 
  rr:subjectMap [
    rr:termType rr:BlankNode;
    rr:template "dummy";
  ].

The result is what I need:

@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix dcterms: <http://purl.org/dc/terms/> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .

<http://www.disney.com/id/cartoons/1>
        a                 disney:Cartoon ;
        rdfs:label        "Mickey Mouse" ;
        dcterms:modified  "2019-12-05T09:26:49Z"^^xsd:DateTime .

<http://www.disney.com/id/cartoons/2>
        a                 disney:Cartoon ;
        rdfs:label        "Donald Duck" ;
        dcterms:modified  "2019-12-05T09:26:49Z"^^xsd:DateTime .

I do not exactly understand why, but now the result contains dcterms:modified properties based on the updated element. 😉

In addition, because the collection only maps to a (dummy) blank node, it does not appear in the result (if needed we can add a PO map for the source attribute).

[pmaria]

I do not exactly understand why [...]

Neither do I 😕. It seems that that Saxon does something smart under the hood whereby it can detect that the DOM Node that is the result of the /cartoons iterator is the parent of the DOM nodes that are the result of the /cartoons/cartoon iterator. Even though they are created separately.

I'll try to dig a bit deeper when I get a chance.

Cool that it works, but I would be hesitant to rely on this since it is not a supported feature 😬

[rorlic]

I understand but I need the dcterms:modified and I cannot change the source.
Since it is working this way, I have no way of knowing if another (more correct) way would work or if this is still the result of this Saxon "feature".

[rorlic]

Of course, the real source is not Disney cartoons 😉