Replace long list of namespaces with list of prefixes used when using serialize. #1679
Description
I am wondering why the latest version of rdflib gives me a long list of namespaces when serializing a Graph to JSON-LD. It didn't used to be like that.
return self.graph.serialize(
format=return_format,
context=dict(self.graph.namespaces()),
auto_compact=True
)
The return_format is 'json-ld'. The context in the result is:
"@context": {
"brick": "https://brickschema.org/schema/Brick#",
"csvw": "http://www.w3.org/ns/csvw#",
"dc": "http://purl.org/dc/elements/1.1/",
"dcam": "http://purl.org/dc/dcam/",
"dcat": "http://www.w3.org/ns/dcat#",
"dcmitype": "http://purl.org/dc/dcmitype/",
"dcterms": "http://purl.org/dc/terms/",
"doap": "http://usefulinc.com/ns/doap#",
"foaf": "http://xmlns.com/foaf/0.1/",
"gtaa": "http://data.beeldengeluid.nl/gtaa/",
"non-gtaa": "http://data.beeldengeluid.nl/nongtaa/",
"odrl": "http://www.w3.org/ns/odrl/2/",
"org": "http://www.w3.org/ns/org#",
"owl": "http://www.w3.org/2002/07/owl#",
"prof": "http://www.w3.org/ns/dx/prof/",
"prov": "http://www.w3.org/ns/prov#",
"qb": "http://purl.org/linked-data/cube#",
"rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
"rdfs": "http://www.w3.org/2000/01/rdf-schema#",
"schema": "https://schema.org/",
"sdo": "https://schema.org/",
"sh": "http://www.w3.org/ns/shacl#",
"skos": "http://www.w3.org/2004/02/skos/core#",
"sosa": "http://www.w3.org/ns/sosa/",
"ssn": "http://www.w3.org/ns/ssn/",
"time": "http://www.w3.org/2006/time#",
"vann": "http://purl.org/vocab/vann/",
"void": "http://rdfs.org/ns/void#",
"xml": "http://www.w3.org/XML/1998/namespace",
"xsd": "http://www.w3.org/2001/XMLSchema#"
},
This is where the graph and namespace bindings (including some custom ones) were created:
self.graph = Graph()
self.graph.namespace_manager.bind("skos", SKOS)
self.graph.namespace_manager.bind("gtaa", Namespace(self._model.GTAA_NAMESPACE))
self.graph.namespace_manager.bind("non-gtaa", Namespace(self._model.NON_GTAA_NAMESPACE))
Further, in the custom class I add another namespace and triples. Here's a fragment:
self.graph.namespace_manager.bind('sdo', Namespace(self._model.SCHEMA_DOT_ORG_NAMESPACE))
# create a node for the record
self.itemNode = URIRef(self.get_uri(concept_type, metadata["id"]))
# get the RDF class URI for this type
self.classUri = self._model.CLASS_URIS_FOR_DAAN_LEVELS[concept_type]
# add the type
self.graph.add((self.itemNode, RDF.type, URIRef(self.classUri)))
The custom Class is used to read some JSON from a backend system, interpret this and generate RDF for the item. You could see this as a wrapper pattern.
As I wrote in comments to this issue, I had to create some custom function to remove unused prefixes from the context, but that code is not so dynamic:
def remove_unused_prefixes(self):
""" Clean up the long list of namespaces.
"""
context = dict(self.graph.namespaces())
used_prefixes = ['gtaa', 'non-gtaa', 'rdf', 'rdfs', 'sdo', 'skos', 'xml', 'xsd']
return {p: context[p] for p in used_prefixes}
and this is used here:
context_used = self.remove_unused_prefixes()
return self.graph.serialize(
format=return_format,
context=context_used,
auto_compact=True
)
Now I just discovered that the context argument can be left out. This is probably because of recent improvements and integration of json-ld. Well done. But it still gives me the long list. Also, when omitting the context argument the auto_compact=True argument finally gives me a short representation that I wanted, for example: "sdo:datePublished": "2006-02-19",. This is not the case when using this context = dict(self.graph.namespaces()). But, after all I still get the long list of namespace that I aren't used.
Another discovery: when further reducing the number of arguments, I still get JSON-LD, but no context at all in the results.
return self.graph.serialize(
format=return_format
)
To summarize this issue: I would like to get JSON-LD serialization including context, but with a minimal list of (used) prefixes/namespaces in response to this request:
return self.graph.serialize(
format='json-ld',
auto_compact=True
)
I hope provided examples will help.