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Re: additionalType property, vs extending Microdata syntax for multiple types

From: Martin Hepp <martin.hepp@ebusiness-unibw.org>
Date: Wed, 20 Jun 2012 19:46:40 +0200
Cc: public-vocabs@w3.org
Message-Id: <4BD6E520-E329-4459-ADB1-11D512B593F8@ebusiness-unibw.org>
To: Kingsley Idehen <kidehen@openlinksw.com>
Hi Kingsley:

I am basically with you, but note that this is a decision that does not need to be made by the schema.org sponsors in the schema.org spec. There can be a recommendation on what RDF clients should do, but we do not need consensus on this detail to go forward with the additionalType property.

The only place where it may have to be specified is the OWL version of schema.org, but that is not authoritative at this point in time anyway. Plus, it would be perfectly okay to leave the respective axiom out of the OWL version for the moment.

Clients will habe to apply tons of data cleansing and consolidation tasks before consuming RDFa an Microdata raw data anyway, so let's keep this issue as low as possible.

Martin
 
On Jun 20, 2012, at 2:56 PM, Kingsley Idehen wrote:

> On 6/20/12 7:19 AM, Ivan Herman wrote:
>> On Jun 20, 2012, at 13:11 , Kingsley Idehen wrote:
>> 
>>> On 6/20/12 1:01 AM, Ivan Herman wrote:
>>>> Dan,
>>>> 
>>>> Using owl:equivalentProperty is a very strong statement. It does not only mean that, if I use schema:additionalType, this also means rdf:type, but it also means that anybody in the World may decide to use schema:additionalType anywhere where rdf:type is used even if, in fact, the data has nothing to do with schema.org. rdf:type being such a core property of the RDF world, even part of many syntaxes, I am not sure yet what consequences that would lead to.
>>> Nothing harmful. The processors of this kind of relationship already understand what's entailed.
>> I am not sure I understand what you say...
>> 
>> But I think that essentially saying that anybody in the (Semantic Web) world is then allowed to use schema:type instead of rdf:type in any of their data is problematic.
> 
> Yes, it would be. I am not suggesting that. I am claiming that RDF processors that possess reasoning capability typically have the ability to handle owl:equivalentProperty semantics. Ditto rdfs:subPropertyOf semantics.
> 
> 
>> I would greatly prefer not to go down that route. Besides: there is no technical reason to do that, the subPropertyOf relationship fully covers the schema.org use case, and that is what we are talking about...
> 
> Yes, but my point is about the fact that we have subPropertyOf and equivalentProperty relationships that could come into play, not always one or the other.
>> 
>> 
>>>> I think I would prefer simply stating an rdf:subPropertyOf. It covers the schema.org use case, it is enough for RDF savy processors to generate the rdf:type statements and it does not do anything more.
>>> But, I doubt the existence of RDF savvy processors that handle rdfs:subPropertyOf while not being able to handle owl:equivalentProperty. At the end of the day, isn't this all about creating a feature for processors that handle multiple vocabularies without disrupting pure microdata processors that don't care about fine-grained semantics of relationships?
>>> 
>> Yep. That is the use case. And I think it is good practice to use the minimally necessary technical definition that covers that use case. And that is subPropertyOf
> 
> It isn't, at least not in my world view. If a property is equivalent to rdf:type, that exactly what it is: equivalent .
> 
>> 
>> 
>>>>  Besides, while there might be many tools out there in the Linked Data space that do such basic RDFS reasoning already, the number of processors that understand the OWL terminology might be much less frequent.
>>> In my experience rdfs:subPropertyOf and owl:equivalentProperty are typically supported re. basic reasoning by RDF processors that offer basic reasoning functionality .
>>> 
>>>> Another issue came up during the discussion, but is much more general. Ideally, it would be nice to get, via content negotiation, an RDF file at http://schema.org (in Turtle and/or RDF/XML) that would include this and other possible statements on the Schema Vocabulary. It would be helpful 'following your nose' for the vocabulary, RDFa processors may use it to expand on the schema terms, etc.
>>> +1
>>> 
>>> Or, simply refer to said resource via <link/> in <head/> should content negotiation be problematic.
>> That would not help an RDFa processor, for example, which typically issues a GET on the vocabulary URI with a preference for Turtle files...
> 
> You can have many <link/> based relationships in <head/> . They can point to different kinds of resources including XHTML resources holding RDFa.
> 
> Please note, I am simply seeking unobtrusive compatibility here. I prefer to give machines and humans choices rather than mandates.
> 
> Kingsley
>> 
>> Ivan
>> 
>> 
>> 
>> 
>>>>  additionalType subProperty may then be part of that file, but, for example, similar statements could be added to bind the schema.org rNews terms to the non-schema versions (b.t.w., that may be a good use case for equivalentProperty), or if, at some point, there is a similar mapping of DC terms to schema.org.
>>> +1
>>> 
>>> Kingsley
>>>> Cheers
>>>> 
>>>> Ivan
>>>> 
>>>> 
>>>> On Jun 19, 2012, at 19:24 , Dan Brickley wrote:
>>>> 
>>>>> Thanks everyone. Lots of mail!
>>>>> 
>>>>> I have tried to make a brief summary of some of the points in the Web
>>>>> Schemas wiki, just a sketch of individual positions really rather than
>>>>> a summary of the whole debate. I also started there to write up
>>>>> details of a concrete proposal for 'additionalType'.
>>>>> 
>>>>> http://www.w3.org/wiki/WebSchemas/additionalTypeProposal ...
>>>>> 
>>>>> Since nobody has volunteered to lead an effort to get Microdata syntax
>>>>> changed to support multiple types from different vocabularies, and on
>>>>> balance after reading thru all the debate, I think we should go for
>>>>> the new property approach.
>>>>> 
>>>>> I'd like to make sure that we capture all the concerns people have in
>>>>> the Wiki and in the resulting property definition, and to give some
>>>>> thought to how validators and checkers ought to behave.
>>>>> 
>>>>> Peter, Egor, others, ... can you live with a new property here? (one
>>>>> of 'additionalType' or 'type') Any preferences on name?
>>>>> 
>>>>> cheers,
>>>>> 
>>>>> Dan
>>>>> 
>>>> ----
>>>> Ivan Herman, W3C Semantic Web Activity Lead
>>>> Home: http://www.w3.org/People/Ivan/
>>>> mobile: +31-641044153
>>>> FOAF: http://www.ivan-herman.net/foaf.rdf
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>> 
>>> -- 
>>> 
>>> Regards,
>>> 
>>> Kingsley Idehen	
>>> Founder & CEO
>>> OpenLink Software
>>> Company Web: http://www.openlinksw.com
>>> Personal Weblog: http://www.openlinksw.com/blog/~kidehen
>>> Twitter/Identi.ca handle: @kidehen
>>> Google+ Profile: https://plus.google.com/112399767740508618350/about
>>> LinkedIn Profile: http://www.linkedin.com/in/kidehen
>>> 
>>> 
>>> 
>>> 
>>> 
>> 
>> ----
>> Ivan Herman, W3C Semantic Web Activity Lead
>> Home: http://www.w3.org/People/Ivan/
>> mobile: +31-641044153
>> FOAF: http://www.ivan-herman.net/foaf.rdf
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
> 
> 
> -- 
> 
> Regards,
> 
> Kingsley Idehen	
> Founder & CEO
> OpenLink Software
> Company Web: http://www.openlinksw.com
> Personal Weblog: http://www.openlinksw.com/blog/~kidehen
> Twitter/Identi.ca handle: @kidehen
> Google+ Profile: https://plus.google.com/112399767740508618350/about
> LinkedIn Profile: http://www.linkedin.com/in/kidehen
> 
> 
> 
> 
> 

--------------------------------------------------------
martin hepp
e-business & web science research group
universitaet der bundeswehr muenchen

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Received on Wednesday, 20 June 2012 17:47:07 GMT

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