[DDI-SRG] Single child Reference element in referenecs

[Joachim Wackerow]

Pascal and others,

What are now the reasons for removing the ReferenceType again?
We should collect the pro/cons and record them in Mantis. So a decision
is later comprehensible.
I have the impression, that the decision regarding this issue is
dependent which persons are attending the meeting :) .


106 elements (22 in reusable, 84 in others) in the current Schema are
reference elements, i.e. they are now using ReferenceType.

Some thoughts regarding the processing of references:
(I have the impression that some of these thoughts have open ends)

References are heavily used in DDI 3.0. Therefore the processing of
references should be easy and clear, and should have a good performance.
Every detail will affect the complexity of the XML document, the
complexity of an XSLT stylesheet, and the processing performance as well.

As the references and identification will be used heavily in a DDI 3
document, XSLT keys seem to very important for processing both. A
construction of a key based on a defined element like ReferenceType or
IdentifiableID seems to be straight forward (the construction of the URN
is complicated anyway). A construction of a key for references which are
represented by 106 different elements is a lot of work. I don't see an
easy way. I'm asking myself for what this can be really useful. It is 
not as necessary as for identifications. But without this possibility I 
have a bad feeling. I think references are in DDI 3 so important. 
Probably there will be an application requirement to identify easily 
references. So the suggested attribute "isReference" with a fixed value 
"true" should be at least realized.

Then a key must be constructed with "//*[@isReference='true']". This is 
an XPath expression which makes a filter test on every element. It is 
very costly when processing large documents to go over EVERY element. 
Furthermore filter tests are not really quickly processed. DDI 3 
documents will be large. This approach can make only sense with keys, 
then this process is necessary only once.

When ReferenceType is not available every referencing element needs an
own template, which can call a general template for processing the
reference details.

What is really the problem with the current explicit reference solution? 
It can be only the size of the document, the complexity is not really 
larger for applications.

I was wondering if the complexity of an XSLT stylesheet can be reduced
in using a generic approach for references, so not for each of the 106
referencing elements an own template will be necessary. This can make
sense in a generic reporting tool using a data-driven approach (push
approach). This approach could make also use of the systematic names of
the referencing elements and/or a look-up table with the field-level
documentation.

Thinking this one step further a general reference container can make
sense, where the referenced subject is defined in an attribute or a
child element. For example instead of UniverseReference,
Reference/ReferencedSubject=Universe.


BTW "//*[URN|ID]" will not work. This would catch also the
identification. Something would be necessary like:
//*
[ local-name() != 'MaintainableID' ]
[ local-name() != 'VersionableID' ]
[ local-name() != 'IdentifiableID' ]
[ r:URN | r:ID ]
This would result in five test on every element.

The function 'ends-with' is only available in XSLT/XPath 2.0. XSLT 1.0
cannot be used again. Only one processor (Saxon) does exist for XSLT
2.0. This seems to be a limiting approach.

This is a general note:
I would prefer data-driven processing of the complex DDI documents
and let do the XSLT processor the work, i.e. element-specific templates,
not a declarative programming style. The schema should be constructed 
accordingly when possible.

Any response welcome.

I'll be available again starting at the meeting September 20.

  Achim

I-Lin Kuo wrote:
> I would even go so far as to say that @isReference is redundant.
> 
> I vaguely recollect that the reason given for the Reference was to 
> identify elements of ReferenceType via a test of //*[Reference]. It 
> didn't convince me at the time, as I think that with the elimination of 
> the extra Reference element, //*[ends-with(local-name(),'Reference')] 
> would work, or //*[URN|ID].
> 
> On 9/7/07, *Pascal Heus* <pascal.heus at gmail.com 
> <mailto:pascal.heus at gmail.com>> wrote:
> 
>     Achim, I-Lin:
>     we reviewed yesterday bug #2
>     (http://mantis.ddialliance.org/view.php?id=2) related to the extra
>     */Reference element that appears under every referencing type in the
>     current schema. We had a general agreement that this is not necessary
>     and that it should be removed or possibly replaced with a fixed
>     @isReference attribute. Since I believe you initially requested this
>     change, we would like to have your perspective on the issue before
>     making a final decision.
>     Would appreciate your prompt input as this change impacts most of the
>     ongoing tool development and the earlier we can make it happen, the
>     better.
>     many thanks
>     Pascal
> 
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> 
> 
> 
> 
> -- 
> I-Lin Kuo
> 
> 
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