use the default namespaces in generating context for json-ld output from rdflib

[satra]

import rdflib as rl
g = rl.Graph()
g.bind('ex', 'http://example.org/')
g.bind('ex2', 'http://example2.org/')
g.add((rl.term.URIRef('http://example.org/a'), rl.RDF.type, rl.term.URIRef('http://example2.org/a')))
print(g.serialize(format='turtle').decode())
print(g.serialize(format='json-ld').decode())

returns

@prefix ex: <http://example.org/> .
@prefix ex2: <http://example2.org/> .
@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#> .

ex:a a ex2:a .

and

[
  {
    "@id": "http://example.org/a",
    "@type": [
      "http://example2.org/a"
    ]
  }
]

it would be nice if the default prefixes could automatically be used for generating the context internally.

[jpmccu]

It's actually very simple to provide it yourself using the namespaces() function on Graph:

import rdflib
g = rdflib.Graph()
g.load('http://www.w3.org/People/Berners-Lee/card.rdf')
# set the context to a dictionary construction from g.namespaces():
print g.serialize(format='json-ld', context=dict(g.namespaces()))

I'm not arguing for or against making this default behavior (it already is in other namespaced formats), but it is very simple to do on your own.

[Swannbm]

Issue #95 has been closed because this one (#43) was running, and this one is closed because the #95 references it.......... and the context still has to be put manually... sad.

[akuckartz]

@Swannbm Wrong, this issue is still open.

[Swannbm]

.....oh.... Forgive me please, I thought it was closed by cmaumet in 2016. Still new on Github.