In the association object returned, the subject will be the disease, and the object will be the model. The model may be a gene or genetic element.
If the query disease is a general class, the association subject may be to a specific disease.
In some cases the association will be direct, for example if a paper asserts a genotype is a model of a disease.
In other cases, the association will be indirect, for example, chaining over orthology. In these cases the chain will be reflected in the evidence graph
- TODO: provide hook into owlsim for dynamic computation of models by similarity