Can related objects be repeated?

[elrayle]

Service AddRelatedObjectToCollection/Object use the following to add the related object.

parent_collection.related_objects << child_related_object
parent_object.related_objects << child_related_object

Should the following result in related_objects = [object1,object2] OR [object1,object2,object1]

        Hydra::PCDM::AddRelatedObjectToObject.call( subject, object1 )
        Hydra::PCDM::AddRelatedObjectToObject.call( subject, object2 )
        Hydra::PCDM::AddRelatedObjectToObject.call( subject, object1 )

Right now, it results in the later.

See test hdra/pcdm/services/collection/add_related_object_spec.rb xit 'should NOT allow related objects to repeat'

See test hdra/pcdm/services/object/add_related_object_spec.rb xit 'should NOT allow related objects to repeat'

[tpendragon]

#related_objects returns doubles? That seems unlikely, I'd expect #ordered_related_objects to do that

[escowles]

The model doesn't really say anything about whether there can be multiple instances of an item in the related_objects (though it does say that they're not ordered). I don't remember a use case for multiples, though in this case it looks like it would be easier to allow them, right?

[elrayle]

From my talks with others, I am under the impression that related_objects are not ordered and therefore should do not repeat. That said, they are created as indirect containers via ActiveFedora::Aggregation which does allow for ordering. So we would have to do something to prevent the ordering.

Perhaps they should be created as direct containers.

[escowles]

I'm not sure that using DirectContainers changes anything: if we're using proxies, then you can have multiple proxies referring to the same item, unless we go out of our way to prevent that.

Maybe we need a validator to check whether the item is already in the related_objects list, and reject duplicates?