- From: <martin.hepp@ebusiness-unibw.org>
- Date: Wed, 7 May 2014 02:06:52 +0200
- To: "Ralph TQ [Gmail]" <rhodgson@topquadrant.com>
- Cc: Simon Spero <sesuncedu@gmail.com>, "Paul J. Keller" <Paul.J.Keller@nasa.gov>, Dan Brickley <danbri@google.com>, Jason Douglas <jasondouglas@google.com>, Aaron Bradley <aaranged@gmail.com>, Mike Bergman <mike@mkbergman.com>, Jay Myers <jay.myers@bestbuy.com>, W3C Web Schemas Task Force <public-vocabs@w3.org>
Hi Folks, I do not know whether this helps in these decisions, but I am seriously considering to move GoodRelations from OWL 1 DL to OWL Full in the future, simply because several publisher-friendly patterns (e.g. accepting entities and text for the same property) are outside of OWL DL, yet very valuable. I have tried hard in the past to keep GR in OWL 1 DL, but since the changes introduced by OWL 2 have put GR into OWL 2 Full anyway, I can as well give up the OWL 1 DL doctrine ;-) Best Martin On 07 May 2014, at 01:51, Ralph TQ [Gmail] <rhodgson@topquadrant.com> wrote: > Thank you Simon, > > Release 2.0 had addressed a number of these points. I will reply further when I have checked the specific issues. Concerning dateUnion and numericUnion, I particularly want to explore that further. Union datatypes are a powerful idea. > > On other concerns, we may have to declare some aspects of QUDT to be semantic web “Linked Data” compatible and non-OWL-2 DL. Concerning VAEM, there have been fixes, some time ago, that need to be published, I will look into that. > > Your response deserves a fuller reply, I will find time for that soon, I hope. > > > Ralph > rhodgson@topquadrant.com > > > > On May 6, 2014, at 4:07 PM, Simon Spero <sesuncedu@gmail.com> wrote: > >> There are a number of reasons why the vocabularies at http://qudt.org/ are not legal OWL or RDF. I will outline a few of the problems in the body of the message, and try explain some of the consequences. More detailed justification of the claims for the claims can be found in the appendix. >> >> There are many other issues; I've picked a few examples that are easy to understand for the typical public-vocabs reader, and which show some common structural errors. >> >> I also picked one that let me use an xkcd cartoon. >> >> Issue 1: You can’t use user defined datatypes as the type of a literal >> >> Literals in RDF have data types. For example, “1”^^xsd:integer is the number 1; “1.1”^^xsd:decimal is the number 1.1, which is 0.1 louder. >> >> OWL allows you to define named datatypes. For example, you can define the datatype :wibble that is an xsd:date or an xsd:dateTime or an xsd:string. However, the lexical space (roughly, the set of strings that can go inside the double quotes) for a user defined data type is always empty, so you cannot have a literal “2001-01-01”^^:wibble . >> There are several reasons for this restriction; the most obvious one in this example is that you have no idea what the value of the literal is - is it the Jan 1st 2001? Or is it the string “2001-01-01”? >> >> Why it matters: >> >> RDF takes a very dim view of “ill-typed literals”. If you have a triple whose literal whose character string is not in the lexical space of its data type, and you know about that datatype, that triple is false. Unfortunately, the triples in a graph are asserted to be true. So, if we have an RDF graph that contains: >> >> :fred :hasWibble “2001-01-01”^^:wibble (is true) >> the graph also contains >> :fred :hasWibble “2001-01-01”^^:wibble (is false) >> >> This is a contradiction, and ex falso quod libet (aka the principle of explosion) applies: >> >> >> (https://xkcd.com/704/) >> >> I should note that although having an ill-typed literal is an error, it is semantic, not syntactic. Under the old RDF 1.0 Semantics, the inconsistency wouldn't have kicked in until RDFS derived it. It would still have been an error. >> >> (Claim A) The RDF for VAEM (“Vocabulary for Adding Essential Metadata”) is inconsistent and entails any RDF graph >> >> Corollary: Any vocabularies that import VAEM are inconsistent. This includes all the vocabularies listed in the QUDT catalog. >> >> Issue 2: You can't use rdfs: IRIs as class names in OWL-2 DL >> >> OWL 2 declares certain namespaces as reserved. Names from these namespaces cannot be used as freely as other names in OWL-2 DL ontologies. This includes all the names from the rdfs namespace. >> >> Why this matters: >> >> OWL-2 DL has certain useful properties as an ontology language. >> • It is decidable ; that is, it is always possible to check if an ontology is consistent, find out which classes are subclasses of which other classes, etc. This property is sometimes overrated; it is rarely useful to know that a reasoning task will finish in some finite amount of time, when you need to have an answer in the next five seconds. >> • There are several quite efficient reasoners for OWL-2 DL, and some very efficient reasoners for specified sub-profiles. >> • There are no reasoners for OWL 2 Full. >> • OWL 2 DL Ontologies can mapped to and from RDF. >> • OWL 2 Full Ontologies can only be mapped to RDF; no reverse mapping is defined. >> >> Claim (B): The VAEM RDF file does not define an OWL 2 DL Ontology. >> >> Corollary 1: Any vocabularies that import VAEM are not OWL 2 DL. This includes all the vocabularies listed in the QUDT catalog. >> Corollary 2: The QUDT ontologies have probably not been checked for consistency. This can be inferred from the fact that the ontologies are not consistent. For example, http://qudt.org.tmp/1.1/schema/qudt has a type clash before the end of the ontology header. >> >> Corollary 3: The QUDT ontologies cannot be edited or processed using OWL tooling. >> >> Issue 3: rdf:Property is not a property type in OWL 2 Ontologies >> >> All OWL 2 properties must be of typed as Object Properties, Data Properties, or Annotation Properties. Under the DL restrictions, a property can only be declared as one of the three kinds. Under Full OWL 2, a property can be all three at once. >> >> None of the rules for mapping OWL 2 properties into RDF generate triples of the form *x a rdf:Property. >> >> If Full OWL 2 is used, DataProperty and AnnotationProperty are effectively subclasses of ObjectProperty. Under the OWL 2 RDF semantics, owl:ObjectProperty is equivalent to rdf:Property. >> If for some reason you really, really want to generate a triple from an OWL Ontology that says *x a rdf:Property , you could make an assertion about that the individual *x is a member of the class rdf:Property .This would be strange thing to do, as this triple would automatically be inferred if *x is ever used as a property, and does not bring in to being any kind of OWL property. >> >> Why this matters >> >> The RDF to OWL parsers in OWLAPI (used by tools like Protegé) will try their best (when lax parsing is enabled) to guess what kind of OWL property a bare rdf:Property was meant to be. This works well in some cases, but it is something of a matter of luck - the parser is attempting to do its best with an invalid owl file. >> >> Strict parsers will fail if a property with no valid OWL property type is encountered. All parsers will discard any rdf:Property triples. >> >> If you want to have an OWL Ontology stored in RDF which can be loaded and processed by OWL tools, don't type properties as just rdf:Property. >> >> If you need a property whose value can be either a datatype or an object, either declare it as an annotation property (if you don't need to reason with it), declare it as an Object Property (if you don't need to write any datatype Axioms about it), or declare it as an Object and Data Property. >> >> If you need to load and save an OWL 2 Full Ontology, do not use RDF; use the Functional Style Syntax (FSS), which can handle non-DL ontologies. >> >> Claim (C): The VAEM RDF file is either not generated from an OWL 2 Ontology, or that Ontology contains unnecessary class assertions. >> Corollary 1: RDF generated by non OWL tools can be difficult to work with in an OWL based tool chain. >> >> Simon >> >> Appendix >> >> Claim (A): The RDF for VAEM (“Vocabulary for Adding Essential Metadata”) is inconsistent and thus entails any other graph. >> >> (1) The OWL-2 Abstract Syntax and Functional Style Syntax Specification, (hereafter OWL2 AS/FSS), §9.4, states that: >> >> "[a] datatype definition DatatypeDefinition( DT DR ) defines a new datatype DT [...] The datatypes defined by datatype definition axioms support no facets so they must not occur in datatype restrictions. Furthermore, such datatypes have empty lexical spaces and therefore they must not occur in literals.” >> >> (2) The OWL 2 Web Ontology Language Mapping to RDF Graphs (hereafter OWL2RDF), §3 states that a triple of the form >> >> (a) *:x rdf:type rdfs:Datatype . >> >> corresponds to the OWL declaration >> >> Declaration( Datatype( *:x ) ) >> >> And that a triple of the form >> >> (b) *:x rdf:type owl:Ontology . >> >> corresponds to an OWL ontology header of the form >> >> Ontology( *:x … ) >> (3) The RDF Semantics specification (hereafter RDF-MT) §7 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 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 notes that a D-unsatisfiable graph entails any other graph by the principle of ex falso quodlibet [xkcd]. >> >> For more details see e.g. the discussion on the principle of non-contraction in the Stanford Encyclopedia of Philosophy: Classical Logic, §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) □ >> >> Claim (B): VAEM cannot be mapped to an OWL 2-DL Ontology. >> >> To pick a single example: >> >> (14) OWL2 AS/FSS, §2.4 declares all IRIS from the rdfs: namespace to be part of the reserved vocabulary. >> (15) OWL2 AS.FSS, §5.1 states that: >> "IRIs from the reserved vocabulary other than owl:Thing and owl:Nothing must not be used to identify classes in an OWL 2 DL ontology.” >> (16) OWL 2 RDF §3.2.5, requires the subject and object of an rdfs:subClassOf triple to refer to class expressions. >> >> The VAEM document contains the following triple: >> >> (17) vaem:numericUnion rdfs:subClassOf rdfs:Resource. >> >> (18) The VAEM document uses an IRI from the reserved rdfs namespace to identify a class, and hence does not represent an OWL 2 DL ontology (17,16,15,14) □ >> Claim (C): The VAEM RDF file is either not generated from any OWL 2 Ontology, or that Ontology contains unnecessary class membership or property assertions. >> >> Following the conversions of OWL 2 RDF §2, let: >> >> >> • a denote an individual >> • OP denote an object property >> • AP denote an annotation property >> • C denote a class; >> • CE denote a class expression >> >> (19) No rule in OWL 2 RDF §2 mentions rdf:Property. >> >> (20) The only rules that can generate a triple whose predicate is rdf:type and whose object is is not directly mentioned in §2 are: >> (a) ClassAssertion( CE a ) ==> >> T(a) rdf:type T(CE) . >> (b) AnnotationAssertion( AP as av ) ==> >> T(as) T(AP) T(av) . >> (c)ObjectPropertyAssertion( OP a1 a2 ) ==> >> T(a1) T(OP) T(a2) . >> (d)ObjectPropertyAssertion( ObjectInverseOf( OP ) a1 a2) ==> >> T(a2) T(OP) T(a1) . >> (21) Named things map to their names. >> (a) T(a) ==> a. >> (b) if CE is a named class, T(CE)= T(C) ==> C >> (c) T(AP) ==> AP >> (d) T(OP) ==> OP >> >> (22) The VAEM RDF contains the triple: >> vaem:ownedBy rdf:type rdf:Property. >> >> (23) The VAEM RDF does not contain any other triple matching >> vaem:ownedBy rdf:type ?TYPE. >> >> (24) IF the VAEM RDF was generated from an OWL Ontology, that Ontology contains at least one of the following assertions (19-22): >> (a) ClassAssertion(rdf:Property vaem:ownedBy) >> (b) AnnotationAssertion(rdf:type vaem:ownedBy rdf:Property) >> (c) ObjectPropertyAssertion(rdf:type vaem:ownedBy rdf:Property) >> (d) ObjectPropertyAssertion(ObjectInverseOf(rdf:type) rdf:Property vaem:ownedBy) >> >> (25) The RDFS Schema specification, §3.5, defining rdfs:subPropertyOf, states that: >> A triple of the form: >> P1 rdfs:subPropertyOf P2 >> states that P1 is an instance of rdf:Property, P2 is an instance of rdf:Property and P1 is a subproperty of P2. >> >> (26) The VAEM RDF contains the triple: >> vaem:rdfs:subPropertyOf vaem:ownedBy >> >> (27) The triple vaem:ownedBy rdf:type rdf:Property is entailed by the the semantics of rdfs:subPropertyOf (25,26) >> >> (28) Either the VAEM RDF file was not generated from any OWL 2 Ontology, or that Ontology contains unnecessary class membership or property assertions. (24, 27) □ >> >> References: >> >> [OWL2 AS/FSS]: OWL 2 Web Ontology Language Structural Specification and Functional-Style Syntax: http://www.w3.org/TR/owl2-syntax/ >> [OWL2 RDF]: OWL 2 Web Ontology Language Mapping to RDF Graphs: http://www.w3.org/TR/owl-mapping-to-rdf/ >> [RDF-MT]: RDF 1.1 Semantics. http://www.w3.org/TR/rdf11-mt/ >> [RDFS]: RDF Schema 1.1 http://www.w3.org/TR/rdf-schema/ >> >> >> >> On Sat, May 3, 2014 at 8:31 PM, Ralph TQ [Gmail] <rhodgson@topquadrant.com> wrote: >> Simon, >> >> Release 2.0 of QUDT is a significant change of 1.0, incorporating all of ISO 80000 and with naming and identifier compliance to NIST SP811 . Before we can release 2.0, NASA needs to approve the editorial review of the NASA QUDT Handbook that you see mentioned in the presentation below. When can the release be expected? I would say sometime in June. This will be done as a set of schemas and some of the unit and quantity graphs. >> >> There is a presentation on QUDT release 2.0 at scribe.com/ralphtq - http://tinyurl.com/om9u6o5 >> >> >> >> A colleague of mine forwarded the recent post of yours at W3C. I’d like to know what you see as invalidating RDF? >> >> This is very strange because we work with QUDT as an RDF/OWL ontology set. >> >> Someone pointed out the way we use numericUnion and dateUnion caused problems with an OWL reasoner. Maybe this is an issue? >> >> You know that there are a number of schemas that make up QUDT? Each schema graph has its own base URI with OWL versioning. >> >> What level of OWL are you wishing to see in QUDT? It uses OWL classes with axioms for property restrictions. But not class expressions. >> >> -------- Original Message -------- >> Subject: Re: Generic Property-Value Proposal for Schema.org >> Resent-Date: Sat, 03 May 2014 23:35:01 +0000 >> Resent-From: public-vocabs@w3.org >> Date: Sat, 3 May 2014 19:34:33 -0400 >> From: Simon Spero <sesuncedu@gmail.com> >> To: Dan Brickley <danbri@google.com> >> CC: Jason Douglas <jasondouglas@google.com>, Aaron Bradley <aaranged@gmail.com>, kevin.polley@mutualadvantage.co.uk,"martin.hepp@ebusiness-unibw.org" <martin.hepp@ebusiness-unibw.org>, W3C Web Schemas Task Force <public-vocabs@w3.org>, Jay Myers <jay.myers@bestbuy.com>, Mike Bergman <mike@mkbergman.com> >> >> >> On Fri, May 2, 2014 at 3:27 PM, Simon Spero <sesuncedu@gmail.com> wrote: >> >> WRT vocabularies for units and quantities: there's always the NASA/TopBraid QUDT ontology, which seems to be moving on towards a new version. >> >> See http://qudt.org/ >> >> Something I need to clarify: after checking, the schemas currently available on the site are not valid OWL or RDF, so I cannot recommend their use at this time. >> >> Simon >> >> >> >> >> >> >> Ralph >> rhodgson@topquadrant.com >> >> >> >> On May 3, 2014, at 7:12 PM, Simon Spero <sesuncedu@gmail.com> wrote: >> >>> Hi Ralph- >>> I saw that the qudt.org homepage is showing an updated date of this March, so it looks like you're making headway on getting the release out. >>> >>> I was wondering if there are any plans to release an OWL version of the ontologies? >>> >>> Thanks, >>> >>> Simon >> >> >> >
Received on Wednesday, 7 May 2014 00:07:35 UTC