CODEWITHSUNDEEP
graphdbgraph-store-protocol
Rob
Rob

Reputation: 70

Graph Store protocol support in GraphDB

I'm having troubles with using the Graph Store protocol, as documented in GraphDB's help section (the REST API docs). Specifically, I have two issues:

  1. The Graph Store protocol is supposed to support PUT requests (see https://rdf4j.org/documentation/reference/rest-api/), but the GraphDB REST API documentation only indicates GET, DELETE and POST operations (when listing all operations under "graph-store" section of the docs)

  2. The notion of "directly referenced graph" does not seem to be working, not sure if I'm doing something wrong. What I tried is:

Step1. I created repository myrepo and included a named graph with the IRI http://example.org/graph1

Step2. I tried to access the graph by including various forms of its IRI in the URL. None of the following works:

http://localhost:7200/repository/myrepo/rdf-graphs/graph1
http://localhost:7200/repository/myrepo/rdf-graphs/http://example.org/graph1
http://localhost:7200/repository/myrepo/rdf-graphs/http%3A%2F%2Fexample.org%2Fgraph1

Also, the "Try it out!" button provided in the REST API docs under each operation reports Bad Request if I try to fill those boxes (repository=myrepo, graph=graph1)

Any ideas how this feature can actually be used? Is there a specific way of writing the "directly referenced named graph" in the request URL? (perhaps GraphDB generates some resolvable identifiers for each named graph? how would they look like?)

Upvotes: 1

Views: 527

Answers (2)

Pavel Mihaylov
Pavel Mihaylov

Reputation: 361

The SPARQL 1.1 Graph Store HTTP protocol is often misunderstood, particularly the notion of "directly referenced graph". When you call the protocol with a URL like http://localhost:7200/repository/myrepo/rdf-graphs/graph1 you literally provide a named graph identified by the whole URL, i.e. your named graph would be "http://localhost:7200/repository/myrepo/rdf-graphs/graph1" and not just "graph1". Consequently you can't use a URL like "http://localhost:7200/repository/myrepo/rdf-graphs/http://example.org/graph1" and expect that the protocol will interpret this as addressing the named graph "http://example.org/graph1". The protocol also supports "indirectly referenced graphs", which is the only way to use a graph URI that isn't derived from the URL used to call the protocol. Please see https://www.w3.org/TR/sparql11-http-rdf-update/#direct-graph-identification for a more detailed explanation.

Because of the above confusion I recommend to avoid using the Graph Store protocol entirely and instead use the SPARQL 1.1 Protocol, which can do everything the Graph Store protocol can except for the convoluted notion of directly referenced graphs. Admittedly the REST API doc "Try it out" feature is broken for some of the Graph Store protocol endpoints.

E.g. to fetch all statements in the named graph http://example.com/graph1 you could do this with curl:

curl -H 'Accept: text/turtle' 'http://localhost:7200/repositories/myrepo/statements?context=%3Chttp%3A%2F%2Fexample.org%2Fgraph1%3E'

To add data to a named graph simply send the data using POST, to replace the data use PUT and to delete the data issue a DELETE request.

This is available in the REST API doc section of the GraphDB Workbench, under "repositories". Note that in the SPARQL 1.1 Protocol URIs must be encircled in < >, unlike in the SPARQL 1.1 Graph Store protocol.

SPARQL 1.1 Protocol in the Workbench REST API doc

Upvotes: 1

Vladimir Alexiev
Vladimir Alexiev

Reputation: 2611

I confirm your observations and posted a bug GDB-5486

  1. instead of POST you could use DELETE then PUT.
  2. For the time being, use "indirectly referenced".

For the record, "indirectly referenced graph" works, and returns various formats, eg:

> curl -HAccept:text/turtle 'http://localhost:7200/repository/myrepo/rdf-graphs/service?graph=http%3A%2F%2Fexample.org%2Fgraph1'

<http://example.org/s> <http://example.org/p> <http://example.org/o> .

> curl -HAccept:application/trig 'http://localhost:7200/repository/myrepo/rdf-graphs/service?graph=http%3A%2F%2Fexample.org%2Fgraph1'

<http://example.org/graph1> {
  <http://example.org/s> <http://example.org/p> <http://example.org/o> .
}

> curl -HAccept:text/nquads 'http://localhost:7200/repository/myrepo/rdf-graphs/service?graph=http%3A%2F%2Fexample.org%2Fgraph1'

<http://example.org/s> <http://example.org/p> <http://example.org/o> <http://example.org/graph1> .

> curl -HAccept:application/ld+json 'http://localhost:7200/repository/myrepo/rdf-graphs/service?graph=http%3A%2F%2Fexample.org%2Fgraph1'
[ {
  "@graph" : [ {
    "@id" : "http://example.org/s",
    "http://example.org/p" : [ {
      "@id" : "http://example.org/o"
    } ]
  } ],
  "@id" : "http://example.org/graph1"
} ]

Upvotes: 0

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