Serializing graph with named graphs

[raffaele...@gmail.com]

Hello,

I'm trying to create a graph containing a number of named graphs and serialize it to trig (and possibly eventually to json-ld).

If I only add quads, they will not be included in the output:

G = ConjunctiveGraph()
g1 = Graph("default", "one")
G.add((URIRef("http://example.com"), RDFS.label, Literal("example 1"), g1))

Full working example is here: https://gist.github.com/raffazizzi/090e0fca05dec01ddeda

If I only create the assertion in the named graph, serializing the main graph yields nothing, understandably.

I only get the correct output when I add both a quad *and* add the same assertion to the named graph, thus duplicating the data (undesirable).

g1 = Graph("default", "one")
G.add((URIRef("http://example.com"), RDFS.label, Literal("example 1"), g1))
g1.add((URIRef("http://example.com"), RDFS.label, Literal("example 1")))

Full working example here: https://gist.github.com/raffazizzi/11f635eb9a6961658c2d

Any ideas on why this is happening? Is it an issue with the trig serializer, or am I misunderstanding how named graphs should work?

Thank you!
Raff

[Drew Perttula]

I'm not sure what you're trying to get with Graph("default", "one").
Graph identifiers are normally URIs, and this seems to work:

from rdflib import Graph, ConjunctiveGraph, Literal, URIRef
from rdflib.namespace import RDF, RDFS
G = ConjunctiveGraph()

G.add((URIRef("http://example.com"), RDFS.label, Literal("example 1"),

URIRef("http://example.com/graph1")))
print G.serialize(format='trig')

@prefix ns1: <http://example.com/> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix xml: <http://www.w3.org/XML/1998/namespace> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

<ns1:graph1> {
<http://example.com> rdfs:label "example 1" .
}

Except for a weird bug where serialize omits the ns1 prefix line the
first time you run it but remembers the line the second time (!)

[Raff]

I see. I was trying to instantiate and populate each graph separately instead of just creating quads. Thanks! Your suggestions brought me in the right direction.

R

[Drew Perttula]

On 03/29/2015 12:06 AM, Drew Perttula wrote:
>
> print G.serialize(format='trig')
>
> @prefix ns1: <http://example.com/> .
> @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
> @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
> @prefix xml: <http://www.w3.org/XML/1998/namespace> .
> @prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
>
> <ns1:graph1> {
> <http://example.com> rdfs:label "example 1" .
> }
>
> Except for a weird bug where serialize omits the ns1 prefix line the
> first time you run it but remembers the line the second time (!)
>
>

https://github.com/RDFLib/rdflib/pull/480 should fix the <ns1:graph1> to
have a prefix line and to not have the <>, which aren't correct for
abbreviated qnames.