Using RDF Shapes to define the schema of Gene Ontology Causal Activity Models
We use OWL as a universal formalism for both ontology development (see https://github.com/geneontology/go-ontology/) and for representing GO-CAMs (the former uses class axioms, the latter uses axioms on individuals, see https://www.w3.org/TR/owl2-primer/ for more info on these terms). The use of ShEx is complementary. OWL encodes "biological truths" and formal encodings of concepts, whereas ShEx is used as a data model constraining the "shape" of GO-CAMs. There are many ways of interconnecting instances in a GO-CAM that are biologically consistent, but we want to constrain these to a common "shape" or structure as this is more predictable for software to deal with.
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