- From: Khalid Belhajjame <Khalid.Belhajjame@cs.man.ac.uk>
- Date: Thu, 04 Aug 2011 17:41:13 +0100
- To: Graham Klyne <GK@ninebynine.org>
- CC: "Cresswell, Stephen" <stephen.cresswell@tso.co.uk>, Luc Moreau <L.Moreau@ecs.soton.ac.uk>, public-prov-wg@w3.org
Hi, I think that derivation *should* be transitive. The counter example that Graham found is indicative of an issue in the definition of derivation and not on its transitiveness. If we look at the definition it states that "Derivation expresses that some characterized thing is transformed from, created from, or affected by another characterized thing." By referring just to the above definition, derivation seems to be transitive. The text in the document tries to be more specific by stating conditions that should be satisfied in order for the derivation to hold. Specifically, the text states that: "From an assertion isDerivedFrom(B,A), the values of some of the attributes B are at least partly determined by the values of some attributes of A". In my opinion, the above statement is incorrect, it states a condition that is stronger to what is needed to express derivation. The condition stated is sufficient for inferring derivation, but it is not necessary. If people insist on bringing attribute values to the picture when talking about derivation, then I would suggest to modify the above text as follows: "If the values of some of the attributes an Entity B are partly or fully determined by the values of some attributes of an another Entity A, then isDerivedFrom(B,A) holds". Thanks, khalid On 04/08/2011 09:35, Graham Klyne wrote: > I observe that this partly answers my earlier response to this > question... but I foresee dragons here. > > #g > -- > > Cresswell, Stephen wrote: >> Luc: >>> Do we want (a form of ) derivation to be transitive? >> >> +1 for having a transitive form of isDerivedFrom. Without that, it is >> not possible to query for "everything that this is derived from" or >> "everything that is derived from this". Perhaps we could have an >> optional stronger form meaning "all of B is derived from A", which would >> surely be transitive. >> >> Stephen Cresswell >> >> -----Original Message----- >> From: public-prov-wg-request@w3.org >> [mailto:public-prov-wg-request@w3.org] On Behalf Of Luc Moreau >> Sent: 29 July 2011 10:56 >> To: public-prov-wg@w3.org >> Subject: Re: PROV-ISSUE-56 >> (derivation-definition-does-not-imply-transitivity): Derivation as >> defined is not transitive [Conceptual Model] >> >> Hi all, >> >> Nice counter-example, Graham! >> >> We have the opportunity to define relationships with the properties >> we want them to have. >> >> Do we want (a form of ) derivation to be transitive? >> >> In the example that Graham provides, do you feel that A has some form of >> >> "influence" on C? >> If so, would you like it to be automatically inferable in the provenance >> >> model? >> >> Regards, >> Luc >> >> >> On 07/29/2011 10:01 AM, Provenance Working Group Issue Tracker wrote: >>> PROV-ISSUE-56 (derivation-definition-does-not-imply-transitivity): >> Derivation as defined is not transitive [Conceptual Model] >>> http://www.w3.org/2011/prov/track/issues/56 >>> >>> Raised by: Graham Klyne >>> On product: Conceptual Model >>> >>> >>> [[ Given an assertion isDerivedFrom(B,A), one can infer that the use >>> of characterized entity denoted by A precedes the generation of the >>> characterized entity denoted by B. ]] >>> Where does this notion of "use" come from in the absence of some >>> referenced activity? >>> >>> Concerning transitivity of derivation: >>> >>> Suppose: >>> A has attributes a0, a1 >>> B having attributes b0, b1 is derived from A, with b0 being dependent >> on a0 >>> C having attributes c0, c1, is derived from B with c1 being dependent >> on b1 >>> So none of the attributes of C can be said to be directly or >>> indirectly dependent on attributes of A, which by the given definition >>> is a requirement for derivation of C from A. Thus, as defined, >>> derivation cannot be transitive. >>> >>> I don't really know if derivation should or should not be transitive, >>> but the above seems to me like a problem of spurious >>> over-specification. My suggestion for now would be to focus on what >>> really matters and see what logical properties fall out later. >>> >>> >>> >>> >> > > >
Received on Thursday, 4 August 2011 16:41:51 UTC