Hi Benny
Is this the model that you are working with?
http://www.disgenet.org/web/DisGeNET/v2.1/rdfIn a case like this where there is a hierarchy within the associations themselves, the best idea is usually to model them as nodes. This gives much more flexibility and richness to the model.
If you have a node for the association, you could then either give it multiple labels, like this:
(g:Gene)<-[:REFERS_TO]-(a:BiomarkerAssociation:GeneticVariationAssociation)-[:REFERS_TO]->(d:Disease)
Node
(a) would have properties and relationships applicable to all BiomarkerAssociations and also those applicable to GeneticVariationAssociations.
Or you could model the relationship type hierarchy as nodes:
(g:Gene)<-[:REFERS_TO]-(ba:BiomarkerAssociation)-[:REFERS_TO]->(d:Disease)
(a)-[:IS_A]->(gva:GeneticVariationAssociation)
Here the association properties and relationships are segregated to the appropriate nodes. Obviously this model allows arbitrary richness if you need to model the complete association ontology.
There is a clear path here from the very simple (a relationship) to the very complex (a hierarchical association model). It's hard to know where to start. I have two pieces of advice: start from a simple model and expect to refactor it as you find out more about your domain and application; base your modelling on real questions that you want to answer, rather than an abstract overview of the complete domain.
Can you articulate a few such questions here?
-Ben