From: Henry Story <henry.story@bblfish.net>

Date: Tue, 8 Feb 2005 19:17:16 +0100

Message-Id: <33601f74c63a24875b492b7a4b2ef740@bblfish.net>

Cc: <semantic-web@w3.org>

To: "Yuzhong Qu" <yzqu@seu.edu.cn>

Date: Tue, 8 Feb 2005 19:17:16 +0100

Message-Id: <33601f74c63a24875b492b7a4b2ef740@bblfish.net>

Cc: <semantic-web@w3.org>

To: "Yuzhong Qu" <yzqu@seu.edu.cn>

I suppose the simple solution would be to just write :relation rdfs:sameAs rdfs:sameAs . but I just found the place in the spec that mentions this <http://www.w3.org/TR/owl-ref/#equivalentProperty-def> I should just say :relation owl:equivalentProperty rdfs:sameAs . Thanks for pointing out those interesting quirks concerning complex properties. Henry Story On 7 Feb 2005, at 09:22, Yuzhong Qu wrote: > Note that a functional property cannot be specified as being > transitive [in OWL DL], it's related to the decidability issue of > reasoning in OWL. > > The OWL S&AS says: > > To preserve decidability of reasoning in OWL Lite (and DL), not all > properties can have cardinality restrictions placed on them or be > specified as functional or inverse-functional. An individual-valued > property is complex if > 1/ it is specified as being functional or inverse-functional, > 2/ there is some cardinality restriction that uses it, > 3/ it has an inverse that is complex, or > 4/ it has a super-property that is complex. > Complex properties cannot be specified as being transitive. > > > > Yuzhong Qu > Dept.Computer Science & Engineering > Southeast University > Nanjing, China, 210096 > > ----- Original Message ----- > From: "Henry Story" <henry.story@bblfish.net> > To: <semantic-web@w3.org> > Sent: Monday, February 07, 2005 4:02 PM > Subject: equivalence relation > > >> >> I am looking for a way to state that a relation is an equivalence >> relation [1]. I want to know this so that I can starting from a graph >> such as >> >> _blank ---relation---> <http://bblfish.net/> >> |------owner-------> "Henry Story" >> >> deduce the graph >> >> <http://bblfish.net> ----owner----> "Henry Story" >> >> >> My thought was that a relation that is functional, symmetric and >> transitive >> is just such a relation. Here is how I come to this conclusion. >> >> 1) Functional and symmetric >> >> If a relation is functional and symmetric, then it is also >> inverse functional. It is a 1 to 1 mapping. >> >> 2) If it is functional, inverse functional and symmetric >> >> then for all aRb we also have bRa >> >> this still allows a and b to be different >> >> 3) if it is transitive then for any a, b and c, where >> >> [1] aRb >> [2] bRc >> >> then >> >> [3] aRc >> >> but since R is symmetric >> >> from [2] bRc we deduce that >> >> [4] cRb >> >> and since R is inverse functional >> >> from [1] aRb and [4] cRb we deduce that a==c >> >> similarly from [3] aRb, [1] aRc and the functional nature of R >> we deduce that c == b. >> >> So a == c and c == b and so a == b. >> >> Is this reasoning ok? >> I was hoping it would be, cause then I can just specify in OWL that >> properties >> are functional, symmetric and transitive if I want them to be >> equivalence relations (or is there a shorthand for this) >> >> Henry Story >> >> [1] http://en.wikipedia.org/wiki/Equivalence_relation >> >> >>Received on Tuesday, 8 February 2005 18:17:33 UTC

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