On 20/01/18 23:51, Claude Warren wrote:
I am working with an RDFConnection to a Fuseki server.
The server is set up as
DatasetGraph serverdsg = DatasetGraphFactory.createTxnMem();
FusekiServer server = FusekiServer.make( 3030, "/ds", serverdsg );
server.start();
I have called
ARQ.enableBlankNodeResultLabels(true);
It seems that the fetch() and query() results for the same graph are
different.
calling
connection.query( "SELECT ?s ?p ?o WHERE { ?s ?p ?o }" )
yields different blank node ID from
connection.fetch();
and
connection.queryConstruct( "CONSTRUCT { ?s ?p ?o } WHERE { ?s ?p ?o }" );
yields a different blank nodes from either of the above.
For the latter two, every call returns new blank nodes.
I'm not sure if this is a defect or an undocumented feature, or perhaps a
bit of both.
I can understand that the "fetch" is different as is simply gets a TURTLE
dump of the db and so the blank nodes might be renumbered. But I would
expect that the construct should return the same node values -- then again,
perhaps not as it is a new model as well.
If this is not a bug (and I am beginning to suspect it isn't) I think the
javadoc should be updated to specify when the
ARQ.enableBlankNodeResultLabels(true); is in play and when it is not.
Correct - this is not a bug. "Result" here means ResultSet.
Adding round-trip handling to models without skolemization (which
changes the RDF itself) would have to be done in parallel to result
sets. It is more work because there are more syntax combinations to
consider.
Mapping labels happens twice: once on the way out (writing) to get
either sort forms like "[:p 123 ; :q 456]" or nice labels _:b0, _:b1,
and once on the way in, parsing the input. Note the "[]" case make
providing blank node labels have a major effect in appearance.
Exposing the iterator versions for CONSTRUCT is possible and non-standard.
For working with remote locations, when you want to round-trip blank
node labels, and remain with formats that still legal standards,
is best restricted to result sets, failing a full, and non-standard,
log protocol (and ideally binary). RDF Patch.
Andy
Claude
