Jan Martin Keil created JENA-2169:
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Summary: Dataset interface should support blank node labels for
graphs
Key: JENA-2169
URL: https://issues.apache.org/jira/browse/JENA-2169
Project: Apache Jena
Issue Type: Improvement
Reporter: Jan Martin Keil
The Recommendations [RDF 1.1
TriG|https://www.w3.org/TR/trig/#sec-graph-statements] and [RDF 1.1
N-Quads|https://www.w3.org/TR/n-quads/#simple-triples] permit blank nodes as
graph labels in datasets. However, this is not supported in Apache Jena. To add
support for blank node labels, the interface
{color:#0747a6}{{org.apache.jena.query.Dataset}}{color} and it's implementing
classes would need new methods corresponding to the following methods:
* {color:#0747a6}{{public Model getNamedModel(String uri)}}{color} -> e.g.
{color:#0747a6}{{public Model getLabeledModel(Resource label)}}{color}
* {color:#0747a6}{{public Dataset addNamedModel(String uri, Model
model);}}{color} -> e.g. {color:#0747a6}{{public Dataset
addLabeledModel(Resource label, Model model);}}{color}
* {color:#0747a6}{{public Dataset removeNamedModel(String uri);}}{color} ->
e.g. {color:#0747a6}{{public Dataset removeLabeledModel(Resource
label);}}{color}
* {color:#0747a6}{{public Dataset replaceNamedModel(String uri, Model
model);}}{color} -> e.g. {color:#0747a6}{{public Dataset
replaceLabelesModel(Resource label, Model model);}}{color}
* {color:#0747a6}{{public Iterator<String> listNames()}}{color} -> e.g.
{color:#0747a6}{{public Iterator<Resource> listGraphLabels()}}{color}
This has real *use cases*: If labeled graphs are used to track the provenance
of statements, as e.g. proposed in the Working Group Note [Data on the Web Best
Practices: Data Quality Vocabulary|https://www.w3.org/TR/vocab-dqv/], minting
an URL is not always appropriate. The current *workaround* is to mint a IRI,
e.g. based on an UUID.
However, there might also be *drawbacks*: The [SPARQL 1.1
Recomendation|https://www.w3.org/TR/sparql11-query/#rGraphRef] permits only
IRIs as graph labels. Graphs with blank node labels might become inaccessible
within SPARQL. But that is probably (didn't test it yet) the same situation as
after importing TriG or N-Quads files with blank node graph labels. (A
shortcoming of SPARQL 1.1 worth to put on [https://github.com/w3c/sparql-12]?)
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