Re: Are there any plans to develop an OWL version of QUDT?

Simon,

On 5/7/2014 6:07, Simon Spero wrote:
> There are a number of reasons why the vocabularies at 
> http://qudt.org/ are not legal OWL or RDF.

They are perfectly legal RDF, but indeed not legal OWL DL. As stated 
elsewhere, not being OWL DL compliant is not necessarily a bad thing.

> *Issue 1:  You can’t use user defined datatypes as the type of a 
> literal *
>

Yes in OWL, but in RDF this is perfectly valid, see

http://www.w3.org/TR/2014/REC-rdf11-concepts-20140225/#dfn-recognized-datatype-iris

"Semantic extensions of RDF might choose to recognize other datatype 
IRIs..."

In the case of QUDT I would even argue that it is of great value to 
create literals such as "4.2"^^qudt:Meter that are a much more 
meaningful information exchange format than "4.2"^^xsd:decimal. Of 
course OWL DL would prohibit this, but OWL DL tools can probably run 
such literals through a normalizer algorithm that also converts feet to 
meters etc. Oh but I forgot... OWL cannot even be used to check if a > b 
or a + b so nevermind.

> *There /are no /reasoners for OWL 2 Full*.

Not true. For example the TopSPIN engine (part of TopBraid Composer Free 
Edition) can run rule on any RDF graph, even with user-defined datatypes 
etc. It's just a matter of writing the right rules. Unless of course you 
mean "Reasoner" = "OWL DL Reasoner", which is not my understanding. On a 
general discussion, see

http://composing-the-semantic-web.blogspot.com.au/2010/04/where-owl-fails.html

> Corollary 3: The QUDT ontologies cannot be edited or processed using 
> OWL tooling.

Not true, they were edited with TopBraid Composer, which is an OWL tool 
(and also an RDF tool).

> *Why this matters*
>
> The RDF to OWL parsers in OWLAPI (used by tools like Protegé) will try 
> their best
>

Proper RDF based tools based on APIs such as Jena or Sesame have no 
problems with these files. You keep coming back to OWL DL compliance, 
and I keep coming back to the fact that it was an (unfortunate) design 
decision by the OWL 2 community and the OWL API to abandon the RDF 
roots. If these design decisions now fire back into RDF and OWL people 
want to enforce their world view upon RDF graphs only because their 
tools cannot handle RDF, then we need to decisively make clear what the 
source of the issue is.

And to be very clear: the OWL DL community has way too long dominated 
ontology development. There is already sufficient value in the basic 
principles of RDF such as URIs and the ability to link anything with 
everything, and the adoption of these simple principles is hindered by 
an overly complex layer cake of features and constraints that few people 
really need. A generation of graduates leaves their universities with 
the impression that the semantic web is OWL DL, and early adopters of 
this technology in industry are overwhelmed by the complexity of the 
whole stack. RDF and SPARQL is really all that is needed to know, and 
with SPARQL's CONSTRUCT you even get a rule language for free (see for 
example http://spinrdf.org).

> (3) The RDF Semantics specification (hereafter RDF-MT) §7 
> <http://www.w3.org/TR/2014/REC-rdf11-mt-20140225/#literals-and-datatypes> states 
> that:
>
>               "[a]n ill-typed literal is one whose *datatype IRI is
>     recognized*, but whose character string *is assigned no value by
>     the lexical-to-value mapping* for that datatype."
>
>     (4) RDF-MT §7.1
>     <http://www.w3.org/TR/2014/REC-rdf11-mt-20140225/#D_interpretations> states
>     that:
>
>         "any triple, and hence any graph, containing an ill-typed
>         literal will be D-unsatisfiable, i.e. false in every
>         D-interpretation. This applies only to literals typed with
>         recognized datatype IRIs in D".
>
>     (5) RDF-MT §7.2
>     <http://www.w3.org/TR/2014/REC-rdf11-mt-20140225/#datatype-entailment> notes
>     that a D-unsatisfiable graph entails any other graph by the
>     principle of /ex falso quodlibet <https://xkcd.com/704/> [xkcd]/.
>
>     For more details see e.g. the discussion on the principle of
>     non-contraction in the Stanford Encyclopedia of Philosophy:
>     Classical Logic, §3
>     <http://plato.stanford.edu/entries/logic-classical/#3>
>
>     The VAEM document at
>     http://www.linkedmodel.org/1.2/schema/vaem includes the following
>     triples:
>
>     (6) http://www.linkedmodel.org/1.2/schema/vaem a owl:Ontology .
>
>     (7) vaem:dateUnion a rdfs:Datatype .
>
>     (8) http://www.linkedmodel.org/1.2/schema/vaem vaem:dateCreated
>     "2011-04-20"^^vaem:dateUnion .
>
>     Proof
>
>     (9) http://www.linkedmodel.org/1.2/schema/vaem is declared to be
>     an owl ontology  (2b,6).
>     (10)     The IRI vaem:dateUnion is declared as a datatype and
>     hence is known(1,2a,7).
>     (11)     Any RDF literal with the datatype IRI vaem:dateUnion is
>     ill typed (1,3,10).
>     (12)     The graph at http://www.linkedmodel.org/1.2/schema/vaem
>     is D-unsatisfiable  (4,8,11).
>     (13)     The graph at http://www.linkedmodel.org/1.2/schema/vaem
>     entails any other RDF graph(5,12)*□*
>

I do not believe these statements are correct. 
"2011-04-20"^^vaem:dateUnion is a perfectly valid RDF literal.

> If a problem falls within the class of problems that OWL 2 DL can 
> handle, it is good to stay within the constraints of DL. Going to OWL 
> Full should be made on a carefully considered basis of costs vs. 
> benefits. 

This is a theory, not a fact. One could argue the other way around: if a 
problem can be solved in RDF Schema, then why use OWL?

> Thirdly: The vocabularies being discussed were inconsistent at every 
> level of the RDF, RDFS, and OWL chain, and contained basic type errors.

I don't see where they were invalid RDF, please clarify.

> I do not know what tools were used to create them, but whatever tool 
> it was could not do basic consistency checking. 

They were created with TopBraid and TopBraid uses Jena which has no 
problems with those files either. Only because they are not valid OWL DL 
does not mean they are inconsistent.

Holger