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Re: Defining subsets of existing OWL / RDF-S vocabularies in another vocabulary?

From: Richard Cyganiak <richard@cyganiak.de>
Date: Mon, 1 Oct 2007 10:32:11 +0200
Message-Id: <E47718AC-CC9D-423C-B063-59F4DD6C383E@cyganiak.de>
Cc: mhepp@computer.org, "Semantic-Web@W3.Org," <semantic-web@w3.org>, "Semanticweb@Yahoogroups.Com," <semanticweb@yahoogroups.com>, Tim Berners-Lee <timbl@w3.org>, Katharina Siorpaes <katharina.siorpaes@deri.at>
To: Alan Ruttenberg <alanruttenberg@gmail.com>

Alan,

On 29 Sep 2007, at 23:33, Alan Ruttenberg wrote:
>> But if you exchange data with the rest of the world, then you'll  
>> have to keep in mind that some agents are web-aware, and will get  
>> their definition of foaf:name from http://xmlns.com/foaf/0.1/name,  
>> and not from your copy, regardless of whatever owl:imports you may  
>> have declared.
>
> An agent that is "web-aware" in such a way as to ignore  
> owl:imports, and retrieve definitions of terms in an OWL ontology  
> from the web would be in variance with the OWL specification. If  
> something is to be fixed, it is the web agent. To build anything to  
> conform to a buggy system is a corrupting influence on the web, vis  
> browser hassles with ensuring compatibility with IE, bugs and all.

OWL is layered on top of RDF and RDFS. There are several agents that  
do not understand OWL, but employ semantic extensions such as follow- 
your-nose and other breadcrumb protocols. These are popular modes of  
operation in the FOAF and LOD communities, and I wouldn't consider  
them “buggy systems”.

If Martin intends to publish his data on the Semantic Web, then I  
think it is good advice to consider the behaviour of such clients. As  
I said before, if he just builds a silo and doesn't intend to publish  
his data, then he does not need to consider this.

>> If you really want to make sure that all agents encountering your  
>> data work off the same vocabulary definitions, then you should  
>> probably duplicate the relevant terms in your own namespace,  
>> creating hepp:name and hepp:knows and so on, and declare them  
>> owl:equivalentProperty to the original terms.
>
> If you really want to make sure that all agents encountering your  
> data work off the same vocabulary definitions, then you need to  
> follow the specification. If we follow the specification, then web  
> agents designers will appreciate  that it is worth learning what  
> the specification says and we will all be better off. If not, we  
> will compound the problem by doing what we think some undocumented  
> web agent wants, because this will undoubtedly violate the  
> undocumented assumptions of some other web agent not following the  
> spec.

Care to point me to *any* Semantic Web agent that does not employ  
some sort of semantic extension of the vanilla specs in order to get  
its job done?

> That said, it has been my practice to define, within my owl  
> ontology, select terms from other ontologies, when I make an  
> assessment that I am not changing the intended meaning of the term,  
> and when importing the full ontology would have undesirable effects  
> - for instance making my ontology OWL-Full, or when the source  
> ontology has bugs that violate their own english definitions, or  
> then the source ontology is too large to import for practical  
> reasons. I'm not suggesting that this is the best idea - time will  
> tell.
>
> YMMV for RDFS, where the means of specifying how definitions are to  
> be retrieved are, at best, loosely specified.

Martin referred to FOAF and DC specifically, both of which are  
designed to work with RDFS-only agents as well as OWL-capable agents.

Richard



>
> -Alan
>
>>
>> Best,
>> Richard
>>
>>
>>>
>>> If that was okay, it would make it easier to prepare pre-composed  
>>> blends of relevant ontologies that can be directly used for form- 
>>> based instance data creation.
>>>
>>> However, I fear that defining an element that is residing in  
>>> someone else's URI space is not okay, since I (e.g. http:// 
>>> www.heppnetz.de) have no authority of defining the semantics of  
>>> an element that is within
>>> |http://xmlns.com/foaf/0.1/, even if I what I am saying is  
>>> consistent with the authoritative definition of the given  
>>> vocabulary element. |
>>> ||
>>> ||I am assuming that I duplicate the very same specification of  
>>> the element, i.e., I would assure that my definition just  
>>> replicates a subset of the official vocabulary. I also abstract  
>>> from semantic dependencies, i.e., whether it is possible to  
>>> specify a consistent subset of a given vocabulary (this may not  
>>> be trivial for an expressive DL ontology, but should be feasible  
>>> for lightweight RDF-S or OWL vocabularies). Also, the legal point  
>>> of view (whether I am allowed to replicate an existing  
>>> specification) is less relevant for me at the moment. I just want  
>>> to know whether this is an acceptable practice from a Web  
>>> Architecture perspective.
>>>
>>> Any feedback would be very much appreciated!
>>>
>>> Best
>>>
>>> Martin
>>> -----------------------------------------------------
>>>
>>> martin hepp
>>> e-mail: martin.hepp@deri.at
>>> web:    http://www.heppnetz.de
>>> skype:  mfhepp
>>> office: +43 512 507 6465
>>>
>>> Check eClassOWL, the first real-world e-business ontology
>>> for products and services in OWL at
>>> http://www.heppnetz.de/eclassOWL
>>>
>>>
>>>
>>
>>
>
>
Received on Monday, 1 October 2007 08:32:40 GMT

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