active_fedora_relsint

h1. ActiveFedora::RelsInt !https://travis-ci.org/projecthydra/active_fedora_relsint.png?branch=master!:https://travis-ci.org/projecthydra/active_fedora_relsint !https://badge.fury.io/rb/active_fedora_relsint.png!:http://badge.fury.io/rb/active_fedora_relsint A mixin for ActiveFedora to allow use and updating of the RELS-INT datastream.

RELS-INT is similar to RELS-EXT: A shallow (depth = 1) XML serialization of a RDF graph. However, the subjects of triples in the RELS-INT graph are an object's datastreams.

For example, consider a Fedora object with a PID of 'test:1' that hold a TIFF image in a datastream called 'content'. You may add various derivative images in additional datastreams, but feel that relying on encoded datastream IDs is too fragile an approach to indicating their relationship to 'content'. You may indicate these relationships in a RELS-INT like the below:

bc. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <rdf:Description rdf:about="info:fedora/test:1/content"> 2400 1600 </rdf:Description> <rdf:Description rdf:about="info:fedora/test:1/ds1"> 150 100 </rdf:Description> <rdf:Description rdf:about="info:fedora/test:1/ds2"> 1500 1000 </rdf:Description> </rdf:RDF>

Then with a supporting ActiveFedora model:

bc. class GenericImage < ActiveFedora::Base include ActiveFedora::RelsInt end

You can identify the thumbnail image by querying the RELS-INT graph:

bc. my_obj = GenericImage.find('test:1') statement = my_obj.rels_int.relationships(my_obj.datastreams['content'],"http://xmlns.com/foaf/0.1/thumbnail").first unless statement.nil? dsid = statement.object.to_s.split('/')[-1] # this will be a RDF::Statement thumb_ds = my_obj.datastreams[dsid] end

You can also add or delete statements to the RELS-INT graph as tested in spec/unit/relsint_spec.rb

Note that the RELS-INT datastream is not able to monitor the object, so datastream deletions would require a seperate removal of the deleted datastreams subgraph in RELS-INT.