- From: Kingsley Idehen <kidehen@openlinksw.com>
- Date: Wed, 25 Apr 2012 14:05:11 -0400
- To: public-rdf-wg@w3.org
- Message-ID: <4F983CD7.2040304@openlinksw.com>
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. +1 Kingsley > > -- 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 >> >> > > > -- 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
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Received on Wednesday, 25 April 2012 18:05:48 UTC