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Re: Correct Usage of rdfs:idDefinedBy in Vocabulary Specifications with a Hash-based URI Pattern

From: Martin Hepp <martin.hepp@ebusiness-unibw.org>
Date: Fri, 22 Oct 2010 06:11:52 +0200
Cc: ML public-lod <public-lod@w3.org>, Tim Berners-Lee <timbl@w3.org>
Message-Id: <460D06F3-3F97-4E3E-8C2B-10CB04733C1A@ebusiness-unibw.org>
To: KangHao Lu (Kenny) <kennyluck@w3.org>
Hi Kenny,

I am inclined towards your position that ontologies (and some other  
resources) don't require a distinction between the entity and the  
specification, because the representation being served is the entity  
in the case of an ontology.

In general I think both practices are acceptable. If anybody knows of  
any compatibility problems caused by using an empty hash as the URI  
reference for the ontology, it would be good to raise his/her voice,  
though.

The most important point is that the identifier used for the ontology  
(owl:Ontology) should be the same as the one used for the  
rdfs:isDefinedBy property.

Best

Martin

On 21.10.2010, at 17:05, KangHao Lu (Kenny) wrote:

> Hello Martin,
>
> I don't think my argument would be very logical, but we can't wait  
> for rule engines to discuss this.
>
>> Note, however, the majority of the Web vocabularies use the same  
>> URI for the entity name reference and the descriptor reference, see  
>> the link provided by Michael Hausenblas:
>>
>> 	http://code.google.com/p/void-impl/issues/detail?id=45
>>
>> and in particular the little survey by Richard Cyganiak posted on  
>> that page.
>>
>> I personally would argue that in the case of ontologies /  
>> vocabularies, the conceptual difference between the entity and the  
>> descriptor is a lot less significant than when it comes to data,  
>> since an ontology is, by definition, a specification, i.e. a  
>> document.
>>
>
> Basically I like this approach, that is, I don't like the fact that  
> some ontologies have '#' as end character and there should not a URI  
> for an ontology document and a different URI for the *conceptual*  
> ontology.
>
> IIRC, 3 years ago Tim was very shocked by those ontologies that have  
> '#' as end charter and claimed that this is not a good idea (and he  
> would bring up this issue at TAG or awwaw, I can't remember). The  
> argument was that string after '#' has the meaning of 'local  
> identifier' (so that we use #I #i for WebIDs because 'I' is a 'local  
> identifier') and identifiers can't be empty strings (or this might  
> break some systems, I guess). I somehow agree with that, and Toby's  
> use of "my:" to identify an Ontology makes me a little bit  
> uncomfortable. I have no idea if there's any followup after Tim  
> brought this to TAG or awwaw.
>
> I have another argument, namely, you should distinguish the concept  
> from the document only if the following criterion is satisfied.
>
> - if the time when the thing with hash URI is created and the time  
> when the document is created have *clear* difference
>
> So this holds for people, so people should not use document URIs.  
> This holds for organizations, cause you create the website of an  
> organization maybe some years after the organization is founded.
>
> The problem is 'ontology'. I don't know whether you should call the  
> structure an ontology or it became an ontology once it is written  
> down, but I don't think the difference of the timing is very  
> *clear*. A similar example is when you want to give a URI to a  
> python module. I would not end it with '#' because I don't see why  
> we need do distinguish the 'module document' from 'module'. A module  
> is a kind of document, so is ontology. So, owl:Ontology  
> rdfs:subClassOf foaf:Document !
>
> Well, this is a theory. If there's a common practice of using '#'- 
> ending URI for ontologies, maybe we should accept it.
>
> No strong opinion. Wasn't this discussed at AWWAW? Just curious.
>
> Cheers,
>
> --
> Kenny
> WebID: http://dig.csail.mit.edu/People/kennyluck#I
> What is WebID: http://esw.w3.org/WebID
Received on Friday, 22 October 2010 04:12:26 UTC

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