Make serialize() on a CONSTRUCT result act like normal g.serialize()

[aucampia]

Discussed in #1612

^{Originally posted by nicholascar June 11, 2021}
Currently (RDFlib 6.0.0a0 AKA master), g.serialize() defaults to turtle format and is decoded, however calling serialize() on a SPARQL CONSTRUCT result (i.e. on a Result object) returns the RDFlib 5.0.0 form of an RDF/XML, UTF-8-encoded result.

The old style serialize() in Result should be updated to match the main Graph() serialize().

[nicholascar]

I'm encountering issues related to this now. I can easily (two word change) make the serialize() return Turtle, not XML, by default, however the result object is still a rdflib.plugins.sparql.processor.SPARQLResult, not a rdflib.graph.Graph and I think it should be a Graph.

The documentation for Result says:

There is a bit of magic here that makes this appear like different Python objects, depending on the type of result.

but the reults aren't real bool, Graph etc objects, as far as I can tell, they are all SPARQLResult objects, but I think they suold be 'pure' bool, Graph etc.

I think it should be a Graph.

Indeed it should be, according to the SPARQL 1.1 spec - “The CONSTRUCT query form returns a single RDF graph specified by a graph template.”

[Priyansh19077]

We are interested in this issue and are currently working on having a way to get the turtle format in the returned results for CONSTRUCT query. We looked into the xmlresults.py file in the reults directory of sparql. We realised that the serialize() function is being called in that file to actually serialize those results.

We are planning to have a way to convert the generated xml statements into turtle and then result that. Another way could be to have a separate file like turtleresults.py and then call the serialize function there.

In case you have any ideas we can go forward with this, please do share them.

[aucampia]

There was a PR for this before:

• Make Result.serialize work more like Graph.serialize #1418

[aucampia]

• While working on Result.serialize() path handling is broken for windows paths and some other cases #2067 I had a bit of a think about Make Result.serialize work more like Graph.serialize #1418, the only breaking change is the default value for encoding, and we can just change this with a very small PR for version 7.0, so I will update that PR slightly to just not change the default encoding.