W3C home > Mailing lists > Public > public-rdf-wg@w3.org > April 2012

Re: regrets and a new spin on contexts

From: Kingsley Idehen <kidehen@openlinksw.com>
Date: Wed, 25 Apr 2012 14:05:11 -0400
Message-ID: <4F983CD7.2040304@openlinksw.com>
To: public-rdf-wg@w3.org
On 4/25/12 1:32 PM, Sandro Hawke wrote:
> On Wed, 2012-04-25 at 18:00 +0100, Thomas Baker wrote:
>> On Mon, Apr 23, 2012 at 12:45:31AM -0700, Pat Hayes wrote:
>>> Second, I have written up essentially the same proposal in a slightly
>>> different terminology which might (?) be more palatable, anyway it is there
>>> for inspection at http://www.w3.org/2011/rdf-wg/wiki/AnotherSpin
>> I like this proposal.  Let me test my understanding of it with reference to
>> some examples "from the wild":
>> 1) As an example of "a named public agreement to use a particular vocabulary of
>>     IRIs... with a particular meaning" consider "Dublin Core in OWL 2" [1] -- an
>>     interpretation of DCMI Metadata Terms undertaken completely independently of
>>     DCMI which offers Turtle and RDF/XML for an "annotation property
>>     version" [2] and an "object and datatype property version" [3] of DCMI's
>>     /terms/ vocabulary, e.g.:
>>      dcterms:dateCopyrighted a owl:AnnotationProperty ;
>>          rdfs:label "Date Copyrighted"@en-us ;
>>          skos:definition "Date of copyright."@en-us ;
>>          rdfs:subPropertyOf dcterms:date ;
>>          rdfs:range rdfs:Literal .
>> 2) Again from the Dublin Core context, an example of what Pat calls
>>     "informally expressed descriptions of constraints":  When the notion of
>>     Application Profile entered DC discourse in 2000, it came to be seen as a
>>     construct which, by definition, only "re-used" terms coined elsewhere (i.e.,
>>     in vocabularies, or "element sets", as they were called).  The purpose of an
>>     Application Profile was to document how a particular application or
>>     community used terms from different vocabularies to meet particular
>>     descriptive requirements.  But what alot of people wanted to do, it turned out,
>>     was to say: "We're using DC Creator, but we're using it specifically for
>>     Composers."  There was alot of discussion to the effect that yes, you can
>>     re-label dc:creator "Composer", but that that does nothing to change the
>>     global meaning of the property.
> In the original Semantic Web vision, they would have defined and used a
> Composer subclass.  Of course, that wouldn't actually work, because they
> couldn't count on anyone (either during data publication or data
> consumption) to do inference.

Yes, but that's a temporary matter. The original vision didn't outline 
the journey sequence as:

1. structured data -- basic Entity-Attribute-Value based data 
representation (using a plethora of syntaxes)
2. structured hyperlinked data (or hyperdata) -- relation semantics have 
low fidelity (just the basics via RDF Schema)
3. reasonable (or reasoner friendly) structured hyperlinked data -- 
relations semantics have high fidelity (OWL).

1-3 still get you to RDF (politely and coherently) while negating a 
minefield of FUD.

>> In both the formal "DC-in-OWL2" case and in many of the less formal
>> "application profile" cases, the authors of these "semantic extensions" (in
>> Pat's sense) replicated definitional information from DCMI's documentation --
>> as in the example above -- presumably in order simply to present self-contained
>> documentation.  There was some discussion to the effect that it would be more
>> elegant (and in principle more maintainable) if the documentation were layered,
>> such that annotations would simply be added to the "canonical" definitional
>> information imported directly from DCMI, but nobody came forward with a
>> convincing method for doing this in practice.
>> Alot of people said they wanted to "extend" Dublin Core, but what this often
>> meant, in practice, was that they wanted to coin more properties.  The notion
>> that application profiles should carefully avoid "extending" existing DC
>> properties semantically was part of this discussion.
>> My point is that these issues basically bubbled up, and they pointed at deeper
>> questions about whether vocabulary owners really do have as much control over
>> the interpretation of their IRIs as we believe they should have in order for
>> the global hypothesis to work in practice.  Even if we don't exactly want to
>> encourage people to make "extensions", it is a good thing to give them a name
>> because this is something that people do.  "Allow[ing] users to be explicit
>> about which semantic assumptions they wish to inherit in their RDF assertions"
>> is a step in the right direction.
> In theory, the advice should be: make your own vocabulary and use OWL to
> tie it to other well known vocabularies.
> Except, as above, since people aren't doing inference, this wont work.
> [ Maybe I need to blog: Why The Semantic Web Hasn't Taken Off:  1.
> Data-consuming software doesn't reliably do inference.  2.  Vocabulary
> IRIs don't reliably lead to great documentation.   ....   What else? ]

Yes, I encourage you to write such a post for sure. In doing so, please  
acknowledge some of the messaging mistakes that have occurred along the 
way. More than anything else, acknowledging mistakes is a nice way to 
reintroduce previously misunderstood initiatives etc..

>> However, I do not like calling these things "semantic extensions".  Pat talks
>> about imposing additional "conditions" or "constraints" on the interpretation
>> of IRIs.  To me, "limiting" and "constraining" are the opposite of "extending".
>> As in the DC discussion ten years ago, the word "extension" hints at things
>> quite different from limiting and constraining (like coining new IRIs).  If the
>> intended scope of "semantic extensions of RDF" is the interpretation of
>> existing IRIs, could we call them something like "semantic annotations" or
>> perhaps "semantic clarifications"?
> How about "ontologies"?

+1 :-)
> I'm amused, but I'm also 100% serious.   An ontology is a set of
> constraints on the meanings of terms.   In some cases, OWL might not be
> the right language to express the ontology -- in some cases, we need 100
> pages of natural language prose.   It's still an ontology.


>      -- Sandro
>> Tom
>> [1] http://bloody-byte.net/rdf/dc_owl2dl/index.html
>> [2] http://purl.org/NET/dc_owl2dl/terms
>> [3] http://purl.org/NET/dc_owl2dl/terms_od



Kingsley Idehen	
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OpenLink Software
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Received on Wednesday, 25 April 2012 18:05:48 UTC

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