Re: Merging RDF graphs

I regret 'cos my level of academic parlance or politenes is low but maybe
this could help: to devise a 'dialog like' protocol which, with kind of
placeholders, could help metamodels (ontologies) to 'negotiate' (message
based functional activation) each other contents. It is briefly described
in this very early / incomplete draft (I'm also sending it as an
attachment). It's a very 'amateur' view of a (mostly) Semantic Web hobbyist:

https://github.com/CognescentBI/BISemantics/blob/master/Document.pdf?raw=true

Best,
Sebastián Samaruga
---
http://exampledotorg.blogspot.com.ar


On Nov 16, 2017 3:57 PM, "Florian Kleedorfer" <florian.kleedorfer@austria.fm>
wrote:

Hi,

As you may recall, I've asked this list about messaging/negotiating using
linked data[1], and it led me and my colleagues to a concept of RDF-based
agreements[2]. (Thanks again for your input!)

Now it's time for us to define how the negotiating parties come up with the
data (set of rdf triples) that they agree on.

One Idea we have is that both particpants (P1,P2) specify 'goals', each
consisting of a SHACL shapes graph and a data graph. Two goals can be
tested for compatibility by merging the two data graphs and then testing if
the resulting graph is valid given the shapes defined by both goals. The
problem we face with this approach is merging the two data graphs. Consider
the example in this gist:

https://gist.github.com/fkleedorfer/81b32e3235105a4a4743e9fa76ba9332

In that example, we would want to merge these two graphs:

ex1:p1g-data {
    ex1:ride1 a taxi:Ride .
    ex1:ride1 taxi:hasDriver ex1:p1 .
    ex1:ride1 taxi:hasPickupLocation ex1:pickup1;
}

and

ex2:p2g-data {
    ex2:myRide a taxi:Ride.
    ex2:myRide taxi:hasClient ex2:p2 .
    ex2:myRide taxi:hasPickupLocation ex2:myPickupLocation .
    ex2:myPickupLocation a s:GeoCoordinates ;
        s:latitude   "48.213814" ;
        s:longitude  "16.340870" .
}

We want that merge to happen in such a way that the shapes in
ex1:p1g-shapes and ex2:p2g-shapes can be evaluated, which will require to
merge some of the nodes. (In the example, we'll find out that a
taxi:hasPickupTime property is missing. One of the participants is then to
add that property, and the whole structure becomes valid according to both
goals' shapes.)

The question is how exactly to achieve that merge. Intuitively, the result
in this case should be

   :mergedNode1 a taxi:Ride .
   :mergedNode1 taxi:hasDriver ex1:p1 . # note: p1 links her own identifier
to the structure
   :mergedNode1 taxi:hasPickupLocation :mergedNode2;
   :mergedNode1 a taxi:Ride.
   :mergedNode1 taxi:hasClient ex2:p2 .
   :mergedNode1 taxi:hasPickupLocation :mergedNode2 .
   :mergedNode2 a s:GeoCoordinates ;
        s:latitude   "48.213814" ;
        s:longitude  "16.340870" .

and after removal of duplicate triples

   :mergedNode1 a taxi:Ride .
   :mergedNode1 taxi:hasDriver ex1:p1 .
   :mergedNode1 taxi:hasClient ex2:p2 .
   :mergedNode1 taxi:hasPickupLocation :mergedNode2 .
   :mergedNode2 a s:GeoCoordinates ;
        s:latitude   "48.213814" ;
        s:longitude  "16.340870" .

(I currently don't care about the URIs of the mergedNodes - just something
one can mint when doing the merge)


Do you have any hints on how to perform such a merge reliably, also with
more complex structures?

Thank you very much in advance!

Best regards,
Florian


Links:
1. Negotiations discussion thread: https://lists.w3.org/Archives/
Public/semantic-web/2017Jul/0004.html
2. Agreements paper: http://ceur-ws.org/Vol-1934/contribution-07.pdf