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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 20:09:00 +0200
Cc: Dan Brickley <danbri@danbri.org>, Peter Mika <pmika@yahoo-inc.com>, jasnell@gmail.com, public-vocabs@w3.org, Ramanathan Guha <guha@google.com>, Jeni Tennison <jeni@jenitennison.com>
Message-Id: <DCC7D832-EAE7-4976-9763-7903973BCC42@ebusiness-unibw.org>
To: Ivan Herman <ivan@w3.org>
Hi Ivan,

On Jun 20, 2012, at 7:01 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.

No. Semantic equivalence does not imply that the property is equally stable, authoritative, or equally understood by clients with limited reasoning support. Using owl:equivalentProperty does not tell people that using either property is perfectly equivalent for annotating data. It just implies that a sufficiently complete OWL environment will accept both ways. There are many clients, notably Google, that do not support OWL or RDFS reasoning, so it is always wise to use the vocabularies that are known to be directly understood by your target audience.

By the way, if you argued from a formal perspective, then rdfs:subPropertyOf would also say that you can always use the more specific property for the more generic one. An in terms of inferences, the result will typically be the very same.


> 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. 
> 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. 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.
> 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. The 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.
> 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

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

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Received on Wednesday, 20 June 2012 18:09:26 UTC

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