add support for OBDA #79
Description
Various data integration challenges may not be easily solved using only a GraphQL schema. Some of these tasks may be addressed using the general approach of custom queries. However, some tasks may instead be addressed using ontologies in a semantic layer. For example, the GraphQL schema cannot easily represent hierarchies between types, or support dynamic views of data. Ontologies, on the other hand, could support arbitrary-depth type hierarchies, ontology-based querying, simplified graph views, inferencing, and mappings to other data sources.
As a first step towards supporting ontology based data access (OBDA), a new module should be created which can generate a GraphQL schema and the corresponding resolver functions based on an OWL ontology and an R2RML mapping file. The generated files should then be integrated into the main woo.sh pipeline. Details remain to be decided.