Re: [rsp] Streaming with TriG?

Our approach should be developed on the abstract RDF model for which TriG is a serialisation.  Once we understand at the abstract level the semantics of our approach we can then define the extensions required for the various serialisations. We should not impose a serialisation if we can avoid it.

Alasdair

On 21 Mar 2014, at 14:12, Manfred Hauswirth <manfred.hauswirth@deri.org<mailto:manfred.hauswirth@deri.org>> wrote:

+1

On 21/03/14 13:47, Daniele Dell'Aglio wrote:
Hi all,
I also like the proposal, but I think that first we should define the
data model, and only after that we should discuss about its
serialization (and here, Trig can be a solution).
Just to make some examples:
- we didn't reach a consensus about how put the timestamps (and how many
timestamps)
- can a stream bring the same graph different times (maybe with
different triples)? I mean, what happens if the the stream contains:
GRAPH :g1{...}  [after some time/elements] GRAPH :g1{...}
- who decide the timestamp(s) associated to a graph? Let's for example
consider a case with one timestamp representing the validity of the
graph. What happens if two streams describes the same graph with
different timestamp values?

So, I really think that we need to understand what is a stream of
graphs, and only after we can discuss about the syntax and how to
implement it.

Daniele

On 03/21/2014 02:21 PM, Roland Stühmer wrote:
Hi Mikko!

I like it. I am using Trig in my streaming system DCEP [1] inside SOAP
messages but also in plain HTTP streaming [3].

https://github.com/play-project/play-commons/tree/master/play-commons-eventformat


By the way an alternative way for a receiver to know when an event
(composed of many triples) is finished we can use HTTP chunked
connections [4]. The connection is long-lived (like a subscription) but
the sender sends a new HTTP chunk for every single event. Start and end
and the size of chunks can be detected by the receiever thanks to pure
HTTP 1.1.

Best!

Roland.

[1] https://github.com/play-project/play-dcep/

[3]
https://github.com/play-project/play-eventadapters/tree/master/play-eventadapter-ldstreams

[4] http://en.wikipedia.org/wiki/Chunked_transfer_encoding


On 21.03.2014 14:11, Mikko Rinne wrote:
Hi, All!

TriG (http://www.w3.org/TR/trig/) reached W3C recommendation status in
February. As it has the basic support for streaming named graphs, there
have been some discussions in our team on whether we should take it into
use. As I haven't seen any discussion on the list or in the RSP CG
minutes on TriG, I was wondering whether there are already strong views
for or against?

For those not familiar with TriG, it is " an extension of Turtle,
extended to support representing a complete RDF Dataset". A couple of
sample events could be represented in TriG like this:

-------------TriG-------------

*

@prefix : <http:example.org/default#> .

@prefix ep:
<http://www.ontologydesignpatterns.org/cp/owl/eventprocessing.owl#> .

@prefix geo:  <http://www.w3.org/2003/01/geo/wgs84_pos#> .


:ev1 { [] a ep:EventObject ;

             geo:Point [ geo:lat 60.158776 ; geo:long 24.881490 ; ] ;

             ep:hasEventObjectSamplingTime
"2014-01-07T09:18:21"^^xsd:dateTime . }


:ev2 { [] a ep:EventObject ;

            geo:Point [ geo:lat 60.187458 ; geo:long 24.821272 ; ] ;

            ep:hasEventObjectSamplingTime
"2014-01-07T09:42:00"^^xsd:dateTime . }


:ev3 { [] a ep:EventObject ;

            geo:Point [ geo:lat 60.187634 ; geo:long 24.821491 ; ] ;

            ep:hasEventObjectSamplingTime
"2014-01-07T10:18:21"^^xsd:dateTime . }

*
-------------------------------

It is not terribly different from doing the same with SPARQL Update:

-----------SPARQL Update-------------

*

PREFIX ep:
<http://www.ontologydesignpatterns.org/cp/owl/eventprocessing.owl#> .

PREFIX geo:  <http://www.w3.org/2003/01/geo/wgs84_pos#> .


INSERT DATA {


 GRAPH <http:example.org/default#ev1> {

          [] a ep:EventObject ;

             geo:Point [ geo:lat 60.158776 ; geo:long 24.881490 ; ] ;

             ep:hasEventObjectSamplingTime
"2014-01-07T09:18:21"^^xsd:dateTime . }


 GRAPH <http:example.org/default#ev2> {

         [] a ep:EventObject ;

            geo:Point [ geo:lat 60.187458 ; geo:long 24.821272 ; ] ;

            ep:hasEventObjectSamplingTime
"2014-01-07T09:42:00"^^xsd:dateTime . }


 GRAPH <http:example.org/default#ev3> {

         [] a ep:EventObject ;

            geo:Point [ geo:lat 60.187634 ; geo:long 24.821491 ; ] ;

            ep:hasEventObjectSamplingTime
"2014-01-07T10:18:21"^^xsd:dateTime . }


} # end-of INSERT DATA

* -------------------------------

The nice thing about TriG is that it would be easier to synchronize in
the middle of a stream (no "INSERT DATA" needed).

Encapsulating streaming objects into graphs has the benefit, as pointed
out earlier by Axel, that the end of the object is explicitly marked.

What do you think?

Mikko




--
Prof. Manfred Hauswirth
INSIGHT Centre for Data Analytics
Digital Enterprise Research Institute (DERI)
National University of Ireland, Galway
http://www.manfredhauswirth.org/


Alasdair J G Gray
Lecturer in Computer Science, Heriot-Watt University, UK.
Email: A.J.G.Gray@hw.ac.uk<mailto:A.J.G.Gray@hw.ac.uk>
Web: http://www.macs.hw.ac.uk/~ajg33
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