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Re: [dxwg] Use of dct:type with both Class and Concept

From: Rob Atkinson via GitHub <sysbot+gh@w3.org>
Date: Mon, 20 Aug 2018 22:55:41 +0000
To: public-dxwg-wg@w3.org
Message-ID: <issue_comment.created-414490039-1534805740-sysbot+gh@w3.org>
@jakubklimek - I think you have summed the underlying issue up with " A typical discovery query is asking for all rdfs:Class and owl:Class instances in a SPARQL endpoint to see what data is there." - we have seen such patterns across a range of platforms - where generally there seems to need to be an implicit contract that the client has some sense of the scope and size of a dataset before issuing a query.  

I would suggest:
1) you could make a tighter query if you only wanted classes with instances - losing expressivitiy without a strong driver and a documented "contract" between producer and consumer is a poor trade-off
2) you should document whats behind an endpoint - "discovery queries" are unsafe (I'm used to spatial and observation data where unbounded discovery queries could return petabytes of data just as easily)
 - RDF datacube and VoiD etc would be a start
3) IMHO Linked Data is about making links replace discovery - making relationships explicit, transparent and dereferenceable as documentation about the link meaning.
4) A client has no means of knowing if inferencing is enabled anyway - so cant really trust any results AFAICT
5) There is a fundamental scalability issue with discovery queries - it might work for a few desktop projects, but there is no evidence I can see that it scales up to either the heterogeneity or numbers of real world.

(I go to a bit of detail here, because this is generally relevant to the drivers for DCAT - ability to describe whats in a dataset and accessible via its end point. My opinion is that if we wanted to consider such an architectural constraint we would need to have a formal documented use case that we can discuss and accept as within scope. I'd be fascinated to see a compelling Use Case for client discovery and access of content starting with, as per your example, an explicit contract that a class model is available at all. If we can see a workable approach it would probably inform us as to the bare minimum MUST have metadata that a dataset description needs to support such an architecture. )



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Received on Monday, 20 August 2018 22:55:47 UTC

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