- From: Adrian Giurca <giurca@b-tu.de>
- Date: Mon, 15 Jun 2015 14:30:48 +0200
- To: Tara Athan <taraathan@gmail.com>, public-rsp@w3.org
- Message-ID: <557EC578.2090104@b-tu.de>
Dear Tara and dear all, Sorry for coming a bit late into the discussion. I would like to stress on the RDF1.1 dataset examples while this is not really a topic for the RSP WG but it may influence its development. Would be a RSP engine allowed to merge graphs? Merging will still allow reasoning about graphs (as introduced by http://wifo5-03.informatik.uni-mannheim.de/bizer/SWTSGuide/carroll-ISWC2004.pdf ) but will also give more reasoning power to any RSP engine. Merging does not disallow a stream engine to use only graph based entailment nor to reason about graphs. Of course, timestamped graphs cannot be merged exactly like not timestamped ones e.g., to merge (ex:g1 time:at "2015-05-30T09:00:00"^^xsd:dateTime") (ex:g2 time:before "2015-06-01T07:00:00"^^xsd:dateTime") would require some effort, possibly a time interval logic (such as Allen Interval algebra http://www.ics.uci.edu/~alspaugh/cls/shr/allen.html ) Sincerely yours, Adrian Giurca On 6/14/2015 12:58 PM, Tara Athan wrote: > Dear Abraham, and all - > Please excuse me if this point has already been discussed in the > group, as I am late joining the discussion. > It seems to me that there is an existing basis on which to build such > a data model - the RDF 1.1 dataset. The semantics for a set of > time-stamped graphs (g_i, p_i, t_i) that seems most appropriate to me > is the one defined here: > http://www.w3.org/TR/rdf11-datasets/#each-named-graph-defines-its-own-context > and the name of each graph would be an implicit blank node that is > also the subject of a triple in the default graph. This triple has > predicate p_i and object t_i . > > Tara > > On 6/14/15 3:59 AM, Abraham Bernstein wrote: >> Dear Emanuele, dear all >> >> I wonder whether we are mixing two issues here. One is the data model >> of time-annotated graphs. The other is a system model that, as you >> indicate, is much easier to deine if you can make some assumptions >> about how the triples (or graph fragments) arrive (in order, >> monotonically increasing, etc.). >> >> I would propose to disentangle the two. In other words, I would >> propose a well-founded time-based data model combined with a set of >> assertions that we expect to hold on streams. >> >> Best >> >> Avi >> >> >> >>> On 12.06.2015, at 18:16, Emanuele Della Valle >>> <emanuele.dellavalle@polimi.it >>> <mailto:emanuele.dellavalle@polimi.it>> wrote: >>> >>> Dear Alasdair, >>> >>> a problem I run into went I implemented the timestamped model in >>> real use cases is that you need to wait for all contemporaneous >>> triples with the same timestamp, before processing them. They arrive >>> to the RSP engine one after each other, so the arrival time is >>> always increasing, but they all carry the some timestamp. If you >>> assume that timestamp are not decreasing, an RSP engine knows it can >>> start the processing as soon as a triple with a larger timestamp >>> arrives, but what if the stream stay silent? How does the RSP engine >>> distinguish the case of a delayed triple (still contemporaneous to >>> those it has already got) from the case it is waiting because >>> nothing is transmitted on the stream? In the C-SPARQL engine we >>> decided to give up with the possibility to treat the application >>> time and we only relay on the receiving time. This is also what >>> STREAM does. It is know as the best effort approach. Esper can work >>> in best effort mode, but you can also send an event to say the time >>> is past. This is call external time control. This time keeping event >>> is a form of punctuation. It means, I told you all I have to say at >>> this point in time. >>> >>> If graphs are timestamped with a strictly increasing timestamp, then >>> as soon as the RSP engine gets the entire graph, it can process it. >>> In other words, the boundary of the graph is a form of punctuation. >>> If another graph with the same timestamp can follow, than you’re >>> back into the problem you cannot distinguish if you are waiting for >>> a delayed graph with the same timestamp from the case the stream is >>> silent. >>> >>> I hope I expressed myself in a clearer way this time. >>> >>> Best Regards, >>> >>> Emanuele >>> >>> PS I’m in favour of multiple time annotations and I agree that >>> interval-based semantics matters. >>> >>> >>> >>> >>>> On 12 Jun 2015, at 18:31, Gray, Alasdair J G <A.J.G.Gray@hw.ac.uk >>>> <mailto:A.J.G.Gray@hw.ac.uk>> wrote: >>>> >>>> Dear Emanuele, >>>> >>>> I don’t quite follow the punctuation argument meaning that we can >>>> only have one graph at any given time point. >>>> (Unfortunately I’m on the train home and cannot access the article >>>> that you linked.) >>>> >>>> We still have the gain over the traditional streaming RDF model in >>>> that all triples conforming to a given observation will be >>>> contained in the graph. So why does having more than one graph at a >>>> given time point cause a problem? >>>> (Sorry if I am missing something obvious) >>>> >>>> Best regards, >>>> >>>> Alasdair >>>> >>>> On 12 June 2015 at 08:49:40, Emanuele Della Valle >>>> (emanuele.dellavalle@polimi.it >>>> <mailto:emanuele.dellavalle@polimi.it>) wrote: >>>> >>>>> Dear Alasdair, and all >>>>> >>>>> thanks for the report. I would like to point out that the sentence >>>>> “There can be multiple graphs with the same timestamp” is, in my >>>>> opinion, a bad choice. It will prevent graphs to be interpreted as >>>>> a form of punctuation [1] and this was one of the most important >>>>> gain of the version of RSP Data Model discussed in Berlin (i.e., >>>>> graphs with strictly increasing timestamps). The lack of >>>>> punctuation is a problem of the “traditional" timestamped triples >>>>> data model where contemporary triples must be admitted. >>>>> >>>>> Best regards, >>>>> >>>>> Emanuele >>>>> >>>>> [1] >>>>> http://link.springer.com/referenceworkentry/10.1007%2F978-0-387-39940-9_285 >>>>> >>>>> >>>>>> On 11 Jun 2015, at 18:37, Gray, Alasdair J G <A.J.G.Gray@hw.ac.uk >>>>>> <mailto:A.J.G.Gray@hw.ac.uk>> wrote: >>>>>> >>>>>> Hi All, >>>>>> >>>>>> During the ESWC RSP Workshop we had a breakout group focus on >>>>>> defining the RSP data model. I was charged with the action of >>>>>> updating the semantics document with the agreed model. >>>>>> >>>>>> You can find the updated data model at >>>>>> https://github.com/streamreasoning/RSP-QL/blob/master/Semantics.md >>>>>> >>>>>> Best regards, >>>>>> >>>>>> Alasdair >>>>>> >>>>>> -- >>>>>> Alasdair J G Gray >>>>>> Lecturer, Heriot-Watt University >>>>>> Web: http://www.alasdairjggray.co.uk >>>>>> <http://www.alasdairjggray.co.uk/> >>>>>> ORCID: http://orcid.org/0000-0002-5711-4872 >>>>>> Twitter: @gray_alasdair >>>>>> Telephone: +44 131 451 3429 >>>>>> Office: EM 1.39 >>>>>> >>>>>> >>>>>> >>>>>> We invite research leaders and ambitious early career researchers >>>>>> to join us in leading and driving research in key >>>>>> inter-disciplinary themes. Please seewww.hw.ac.uk/researchleaders >>>>>> <http://www.hw.ac.uk/researchleaders>for further information and >>>>>> how to apply. >>>>>> >>>>>> Heriot-Watt University is a Scottish charity registered under >>>>>> charity number SC000278. >>>>> >>>> -- >>>> Alasdair J G Gray >>>> Lecturer, Heriot-Watt University >>>> Web: http://www.alasdairjggray.co.uk <http://www.alasdairjggray.co.uk/> >>>> ORCID: http://orcid.org/0000-0002-5711-4872 >>>> Twitter: @gray_alasdair >>>> Telephone: +44 131 451 3429 >>>> Office: EM 1.39 >>>> >>>> >>>> >>>> We invite research leaders and ambitious early career researchers >>>> to join us in leading and driving research in key >>>> inter-disciplinary themes. Please seewww.hw.ac.uk/researchleaders >>>> <http://www.hw.ac.uk/researchleaders>for further information and >>>> how to apply. >>>> >>>> Heriot-Watt University is a Scottish charity registered under >>>> charity number SC000278. >>> >> >> ----------------------------------------------------------------- >> | Professor Abraham Bernstein, PhD >> | University of Zürich, Department of Informatics >> | web: http://www.ifi.uzh.ch/ddis/bernstein.html >> > -- -Adrian Twitter <http://www.twitter.com/giurca> LinkedIn <http://www.linkedin.com/in/adriangiurca>
Received on Tuesday, 16 June 2015 13:38:50 UTC