Re: RSP Data Model

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
>