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From Stian Soiland-Reyes <st...@apache.org>
Subject [RDF] adaptation methods in RDFTermFactory?
Date Tue, 13 Sep 2016 00:56:03 GMT
[[ Cross-post - prefer replies to dev@commons ]]

Each of the Common RDF implementations come with a RDFTermFatory

http://stain.github.io/incubator-commonsrdf/integration/org/apache/commons/rdf/api/RDFTermFactory.html

On a classical flat classloader the implementations of this factory
can be discovered with java.util.ServiceLoader


So if you have say a JsonLdRDFTermFactory you can call .createTriple()
etc - and it would be backed by that implementation. As mentioned the
marker interfaces will allow you to later on get hold of the wrapped
object, e.g. to do some RDFS reasoning on a Jena Model or to parse it
to a serializer.


But what if you already have a 'native' object, e.g. a
org.eclipse.rdf4j.model.Statement - and you want to convert it/adapt
it to the corresponding Commons RDF API Triple?

Obviously there would not be a general interface for this (without
using ?-generics) as each backend implementation would have different
(so far unrelated) types - but we can at least agree on the common
style?

In

http://stain.github.io/incubator-commonsrdf/integration/org/apache/commons/rdf/rdf4j/RDF4JTermFactory.html

I suggests as*() adapter methods like:


RDF4JQuad asQuad(org.eclipse.rdf4j.model.Statement

RDF4JTriple asTriple(org.eclipse.rdf4j.model.Statement statement)

RDF4JTerm asRDFTerm(org.eclipse.rdf4j.model.Value value)

RDF4JDataset asRDFTermDataset(org.eclipse.rdf4j.repository.Repository
repository)

RDF4JGraph  asRDFTermGraph(org.eclipse.rdf4j.model.Model model)

RDF4JGraph  asRDFTermGraph(org.eclipse.rdf4j.repository.Repository repository)


but also the inverse converters:

org.eclipse.rdf4j.model.Value  asValue(RDFTerm term)

org.eclipse.rdf4j.model.Statement
asStatement(TripleLike<BlankNodeOrIRI,IRI,RDFTerm> tripleLike)


(These will unpack the wrapped value if it's an RDF4JTerm - or create
a new RDF4J native instance if it's a "foreign" class)


Questions:


a) Do these adapter methods belong in the RDFTermFactory or should
there be a new family of 'adaptor factories'? (e.g. the Jena Factory


b) What should we call these methods?  Is as*() appropriate or should
they more closely match the createTriple() etc methods from
RDFTermFactory?

With asSomething() I wanted to hint of adaptation - rather than
'convert' or 'create' - but without having to commit to adaptation
with adapt() or wrap().


Now sometimes the implementations use the same class name as Commons
RDF (e.g. Quad or Graph). Code-wise this is not too hard to deal with
(avoid importing either), but it means it can get more confusing for
downstream API users who do auto-complete and then don't know what
direction they are adapting.


c) Should the adapter methods have short names (e.g. asGraph()) -
distinguished by type polymorphism and javadocs - or more verbose to
show which particular return-type you get? (e.g. asJenaGraph() and
asCommonsRDFGraph()) )


d) Do we need to rename RDFTermFactory to RDFFactory (or just RDF) ?



-- 
Stian Soiland-Reyes
http://orcid.org/0000-0001-9842-9718

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