On 01/09/2024 11:57, Bart van Leeuwen wrote:
Hi,
When I do a fetch(graph) on a RDFConnection created by RDFConnectionFuseki
on a fuseki endpoint (4.10.0) and the graph does not exist a 404 exception
is thrown.
I would expect an empty Model, and not an exception?
Doing a fetch on dataset from e.g. stardog to a none existing graph
returns an empty model.
Met Vriendelijke Groet / With Kind Regards
Bart van Leeuwen
(GSP = SPARQL Graph Store Protocol)
"Empty graph" vs "graph does not exist" is murky area because triple
stores using quad indexing don't differentiate between the two cases
leading to inconsistent behaviour. Jena behaviour is supposed to be
consistent for all stores (quad based or not).
As to the effect on GSP GET - what does the community want?
Fuseki is making a special test so teh GSP GET behaviour can be changed
without disturbing anything else.
There are corner cases:
Does "GRAPH ?G {}" include <uri>?
Presumably "no" for all stores - else there are infinite results.
Does "GRAPH <uri> {}" return a row?
Jena - yes. Empty patten on empty graph is one row, no columns.
What does
CREATE GRAPH <uri> ;
CREATE GRAPH <uri>
do?
From an plain HTTP point of view, the URL
http://server/database?graphname=uri
(there is nothing special about query strings when identifying a web
resource) does not exist so 404 is natural when client accesses are not
SPARQL aware.
Checking the spec:
GSP says some at-odds things:
"""
If the RDF graph content identified in the request does not exist in the
server, and the operation requires that it does, a 404 Not Found
response code MUST be provided in the response.
"""
GSP GET says:
"""
It is equivalent to
CONSTRUCT { ?s ?p ?o } WHERE { GRAPH <graph_uri> { ?s ?p ?o } }
"""
which would be empty. Whether the equivalence observation
But GSP POST says
"""
If the graph IRI does not identify either a Graph Store or RDF graph
content, the origin server should respond with a 404 Not Found.
"""
GSP DELETE does say it's 404.
