- From: Krzysztof Janowicz <janowicz@ucsb.edu>
- Date: Wed, 9 Nov 2016 08:53:14 -0800
- To: Joshua Lieberman <jlieberman@tumblingwalls.com>, Rob Atkinson <rob@metalinkage.com.au>
- Cc: Krzysztof Janowicz <jano@geog.ucsb.edu>, Simon Cox <Simon.Cox@csiro.au>, Kerry Taylor <kerry.taylor@anu.edu.au>, Armin Haller <armin.haller@anu.edu.au>, SDW WG Public List <public-sdw-wg@w3.org>
- Message-ID: <8df32b10-d094-d3a0-a979-a8ec2232a15d@ucsb.edu>
> Since owl:Class rdfs:subClassOf rdfs:Class, then any owl class is also > an rdfs class. However, not every rdfs class is an owl class. Yes, at least for OWL1. On 11/08/2016 09:58 PM, Joshua Lieberman wrote: > Since owl:Class rdfs:subClassOf rdfs:Class, then any owl class is also > an rdfs class. However, not every rdfs class is an owl class. > >> On Nov 8, 2016, at 6:47 PM, Rob Atkinson <rob@metalinkage.com.au >> <mailto:rob@metalinkage.com.au>> wrote: >> >> >> Correct me if I'm wrong here: >> >> >> :myClass a owl:Class, rdfs:Class >> >> is the same as >> >> :myClass a owl:Class >> >> if you are using OWL reasoning. >> >> If you are using RDFS reasoning (and tools like RDF4J support this) - >> then these statements are not the same - and only the first one helps >> you with any RDFS reasoning. >> >> So why cant we just use the first form? >> >> The principle would be that the "core" would not _require_ OWL >> reasoning to provide a RDFS model. It doenst mean we don't model in >> OWL, just that we take on the responsibility of materialising OWL >> entailments sufficient to allow any RDFS entailments. (Thats what I >> mean about a "contract" with the user - being explicit about what >> entailments are theer responsibility >> >> >> Note that is we state: >> >> :myClass a rdfs:Class >> >> and say: >> :myClass owl:equivalentClass eg:yourClass >> >> then if you use OWL reasoning you get >> >> :myClass a owl:Class, rdfs:Class >> >> because >> owl:equivalentClass rdfs:domain owl:Class >> owl:equivalentClass rdfs:range owl:Class >> >> Therefore, if you don't explicitly state its an owl:Class you can >> still do OWL reasoning and you have lost nothing - but if you don't >> explicity state its and RDFS class then you wont get the full RDFS >> expressible semantics without OWL reasoning. >> >> statements such as owl:inverseOf are just documentation for RDFS >> interpretations, and perhaps "do no harm"? >> >> am I missing something here? >> >> note that we can then have sosa-owl-dl and other OWL flavours as >> vertical modules that require OWL reasoning to be fully understood. >> >> Rob Atkinson >> >> >> >> >> On Wed, 9 Nov 2016 at 10:01 Krzysztof Janowicz <jano@geog.ucsb.edu >> <mailto:jano@geog.ucsb.edu>> wrote: >> >> Hi, >> >> Sorry for being so picky about this during our meeting but I do >> not want us to take decisions that have consequences that we can >> not yet foresee. >> >> To the best of my knowledge (and please correct me if I am wrong): >> >> Under the semantics of OWL1, rdfs:class and owl:class are only >> equivalent for OWL-Full. For OWL-DL (and OWL-Lite) owl:class is a >> subclass of rdfs:class. >> >> This means that every valid document in OWL will be a valid >> document in RDFS, however *not* every rdfs:class is an owl:class. >> I do not want us to end up in OWL-Full because of this. >> >> For OWL2, I found this: 'owl:Class rdfs:subClassOf rdfs:Class . " >> (https://www.w3.org/TR/owl2-rdf-based-semantics/). Things may be >> more complicated here due to OWL2 punning and they may well turn >> out to be equivalent, I will check this later. >> >> If we decide to restrict ourself to only using RDFS for >> SOSA-core, and I am not in favor of this, then we may have to go >> with rdfs:class. However, we have not yet taken this decision and >> have also not discussed which axioms and language to use for SSN. >> As Sosa-core and SSN will be aligned, this may have more >> consequences that we should consider. It also seems like many of >> us are in favor of using inverseOf, so we would be using OWL (and >> its formal semantics) anyway. Note that this does not do any harm >> to an RDFS-only tool/user as for those the inverseOf axiom will >> simply have no formal semantics. Still all other triples that use >> both relations will still be just fine. >> >> Given the subclasssing, I do not see any problems using >> owl:class, but we may accidentally end up in OWL-full or with >> being incompatible to the standards if we opt for rdfs:class. >> Again, I am happy to be corrected. At least, I do not see harm in >> simply using owl:class. >> >> Finally, and from very pragmatic point of view: ontologies that >> are under very heavy use such as the DBpedia ontology simply use >> owl:class and I have not yet seen any issues or complaints about >> that. See, for example, http://dbpedia.org/ontology/City >> "dbo:City rdf:type owl:Class ." The same is true for the >> goodrelations ontology and so forth (but I admit that this is due >> to the more complex axiomatization they use). >> >> I hope this will start a productive discussion. >> >> Thanks for reading, >> Krzysztof >> >> > -- Krzysztof Janowicz Geography Department, University of California, Santa Barbara 4830 Ellison Hall, Santa Barbara, CA 93106-4060 Email: jano@geog.ucsb.edu Webpage: http://geog.ucsb.edu/~jano/ Semantic Web Journal: http://www.semantic-web-journal.net
Received on Wednesday, 9 November 2016 16:53:50 UTC