- From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
- Date: Wed, 29 Jul 2020 22:48:01 +0200
- To: Patrick J Hayes <phayes@ihmc.us>, Henry Story <henry.story@bblfish.net>
- Cc: Semantic Web <semantic-web@w3.org>
Le 29/07/2020 à 18:52, Patrick J Hayes a écrit : > > [skip] > Ahem. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3199260 Yes. It's important to differentiate between "there is nothing for X" and "there is no *standard* for X". And also differentiate between "there is something for X" and "there is a *standard* for X". In this case, there is a well documented formal semantics for Named Graphs, namely the one that Pat references. It also has the privilege to be the first published formal semantics of Named Graphs. However, not only "Pat's Named Graph semantics" (I'll use this term to denote the semantics defined in Carroll et al.'s paper, that is, the one that Pat references) is not standard, but it also isn't the only one formal semantics for Named Graphs. If a document D1 contains: <x> { <Superman> <kissed> <LoisLane> . <Superman> owl:sameAs <ClarkKent> . } does it say the same thing as document D2: <y> { <Superman> <kissed> <LoisLane> . <Superman> owl:sameAs <ClarkKent> . } ? Or, does D1-union-D2 entails "<x> owl:sameAs <y>". In Pat's Named Graph semantics, it does not. There are good reasons for this, which are explained in Carroll et al.'s paper. Yet, there are also good reasons (arguably) to use Named Graphs with the intent that D1 is equivalent to D2, or that it entails that D1-union-D2 entails "<x> owl:sameAs <y>". Also, if D3 says: <x> { <ClarkKent> <kissed> <LoisLane> . } then, in Pat's Named Graph semantics, it is not the case that D1 entails D3. Yet, there are good reasons (arguably) to use Named Graphs with the intent that D1 entails D3. There are ways of defining a formal semantics for Named Graphs such that D1 entails D2, or that D1 entails D3, or both. These different ways of interpreting Named Graphs (and more generally RDF Datasets) have been discussed ad nauseam in the RDF 1.1 Working Group. The group published a note about these options (https://www.w3.org/TR/rdf11-datasets/), that I authored. Although I authored it, it is not supposed to reflect my personal view on the topic. It is meant to reflect the state of the discussions within the working group, and the extent of the possibilities when it comes to interpreting Named Graphs and RDF Datasets. Now, personally, I have my preference. I would prefer that D1 entails D3, and I think that Pat's Named Graph semantics could be encoded using a different data structure similar to a "named graph literal". For instance: <alice> <likes> "<bob> {<Superman> <kissed> <LoisLane> . <Superman> owl:sameAs <ClarkKent>}"^^pat:NGSemantics . <bob> { <Superman> <kissed> <LoisLane> . <Superman> owl:sameAs <ClarkKent> } would entail: <bob> { <ClarkKent> <kissed> <LoisLane> . } but would not entail: <alice> <likes> "<bob> {<ClarkKent> <kissed> <LoisLane> .}"^^pat:NGSemantics . nor: <alice> <likes> "<nick> {<Superman> <kissed> <LoisLane> . <Superman> owl:sameAs <ClarkKent>}"^^pat:NGSemantics . Opinions may vary. (huho, I think I opened another big can of worms here...) -- Antoine Zimmermann ISCOD / LSTI - Institut Henri Fayol École Nationale Supérieure des Mines de Saint-Étienne 158 cours Fauriel 42023 Saint-Étienne Cedex 2 France Tél:+33(0)4 77 42 66 03 Fax:+33(0)4 77 42 66 66 http://zimmer.aprilfoolsreview.com/
Received on Wednesday, 29 July 2020 20:48:18 UTC