A Haskell function that computes if two RDF graph structures are identical. Uses functions from the rdf4h library and the Automorphism.isIsomorphic function from the hgal library

RDF graph isomorphism in haskell

-- | Compares the structure of two graphs and returns 'True' if their
--   graph structures are identical. This does not consider the nature
--   of each node in the graph, i.e. the URI text of 'UNode' nodes,
--   the generated index of a blank node, or the values in literal
--   nodes. Unsafe because it assumes IRI resolution will succeed, may
--   throw an 'IRIResolutionException` exception.
isGraphIsomorphic :: (Rdf a, Rdf b) => RDF a -> RDF b -> Bool
isGraphIsomorphic g1 g2 = Automorphism.isIsomorphic g1' g2'
  where
    g1' = rdfGraphToDataGraph g1
    g2' = rdfGraphToDataGraph g2
    rdfGraphToDataGraph :: Rdf c => RDF c -> Graph
    rdfGraphToDataGraph g = dataGraph
      where
        triples = expandTriples g
        triplesHashMap :: HashMap (Subject, Predicate) [Object]
        triplesHashMap = HashMap.fromListWith (<>) [((s, p), [o]) | Triple s p o <- triples]
        triplesGrouped :: [((Subject, Predicate), [Object])]
        triplesGrouped = HashMap.toList triplesHashMap
        (dataGraph, _, _) = (graphFromEdges . fmap (\((s, p), os) -> (s, p, os))) triplesGrouped