[jsdl-wg] [Fwd: Proposed extension]

[Michel Drescher]

Donal,

careful, you are mixing two concepts here: intra-document uniqueness and 
inter-document uniqueness.

Donal K. Fellows wrote:
> Peter Lane wrote:
>> I also think the ID attribute is perhaps redundant. JobIdentification  
>> has a JobName element that seems like it should be sufficient for  
>> uniquely identifying a subjob. Or is this not how the authors  
>> envisioned JobName's use?
> 
> Actually, the problem with an ID attribute is more subtle, in that the
> uniqueness constraint upon it is defined purely at the document level.

There is no subtlety with xsd:ID and xsd:IDREF. They are defined exactly 
for what they are supposed to do: intra-document uniqueness. Full stop. 
The proposal never intended to promise more than intra-document 
uniqueness as this is what is required by intra-document dependencies.

> In the world of XML documents living at URLs, the wider disambiguation
> is done by the URL of the overall document, but that's not useful with
> JSDL because job submission templates will typically not have a (fixed)
> URL before the submission. 

Talking about inter-document uniqueness touches the domain of naming, 
which is the topic of another working group, the OGSA-Naming WG.

> I suspect that to fix this we need a GUID
> *somewhere* in there, and that the source of the GUID has to be either
> the user or (more likely) the client software that injects the JSDL
> document into the system. That would allow JSDL consumers to know
> unambiguously whether they've seen the document before without having to
> do a full canonicalize-and-compare. 

All this may be valid issues, but not for the proposal. If you need to 
fix inter-document uniqueness, add a QName to the outermost JSDL 
document element and use an appropriate GUID algorithm that fits the 
QName requirements. Or use the stuff the Naming-WG is proposing.

> With a bit of work[*], I might even
> come up with a scenario where a full comparison would fail despite two
> JSDL documents really being the "same" in some higher-level sense.
> Things get quite complex when you have job rewriting/optimization
> services in the mix, but a GUID lets the "what is identity" decision be
> taken at a the outermost - and hence most abstract - level.

Separate the concerns. Hence separate the mechanisms of JSDL document 
identification and document element identification (to use some other 
terms rather iter- and intra-documennt blah blah).

Cheers,
Michel

-- 
Michel <dot> Drescher <at> uk <dot> fujitsu <dot> com
Fujitsu Laboratories of Europe
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