function to find concise bounded graph for SPARQL Updates

[bblfish]

When a PATCH request using SPARQL Update contains a subject with a blank node, then INSERT DATA and DELETE DATA cannot work ( unless the relation is an owl:InverseFunctionalProperty ). In that case one must calculate the Concise Bounded Description of the graph and put that in the WHERE clause. So one needs to calculate this CBD.

( not checked exactly if CBD is the right relation )

for example in FOAF foaf:mbox is an owl:inverseFunctionalProperty. In that case
the server could in fact delete all the correct blank nodes for the following request

  DELETE DATA { [] foaf:mbox <mailto:henry.story@bblfish.net> . }

But for an graph such as

<#me> contact:home [ a contact:ContactLocation;
                                  contact:address [ contact:city "Fontainebleau";
                                  contact:country "France";
                                  contact:postalCode "77300";
                                  contact:street "21 rue Saint Honore" 
                                ];
             ];
            contact:work [ a contact:ContactLocation;
                             contact:address [ contact:city "Fontainebleau";
                                    contact:country "France";
                                    contact:postalCode "77300";
                                    contact:street "21 rue Saint Merry" 
                              ];
           ];
           contact:work [ a contact:ContactLocation;
                     contact:address [ contact:city "Fontainebleau";
                                  contact:country "France";
                                  contact:postalCode "77300";
                                  contact:street "23 rue Saint Merry" 
                      ];
              ] .

The replacing the postalCode cannot be done like this

DELETE DATA { [] contact:postalCode "77300" }
INSERT DATA { [] contact:postalCode "77305" }

because the server would not know

• which triple in the above graph to remove. ( the one for the home address or the one for the work address ? )
• where to put the new triple ( does it even get attached to an address? )

So really one needs a query such as the following:

DELETE { ?add contact:postalCode "77300" }
INSERT { ?add contact:postalCode "77300" }
WHERE {
    ?add  contact:city "Fontainebleau";
               contact:country "France";
               contact:postalCode "77300";
               contact:street "21 rue Saint Merry" 
}

But this works only because we are here assuming that contact:city, contact:country, contact:postalCode and contact:street form an owl:key .

If these four relations did not form an owl:key then one would have to at leat try to add as many relations to the WHERE clause to make the update identify one object in that particular graph.

[bblfish]

this requires a function of the type

def calculateUpdate[Rdf<:RDF](pg: PiNG, rel: Rdf#URI, oldValue: Rdf#Node, newValue: Rdf#Node): Sparql#Query 

[bblfish]

workaround: Use Conditional PUT