5.2 Extractor Policies
An extractor policy is a named dictionary entity that determines the characteristics of a semantic index that is created using the policy.
Each extractor policy refers, directly or indirectly, to an instance of an extractor type. An extractor policy with a direct reference to an extractor type instance can be used to compose other extractor policies that include additional RDF graphs for ontologies.
The following example creates a basic extractor policy created using the GATE extractor type:
begin sem_rdfctx.create_policy (policy_name => 'SEM_EXTR', extractor => mdsys.gatenlp_extractor()); end; /
The following example creates a dependent extractor policy that combines the
metadata extracted by the policy in the preceding example with a user-defined RDF graph named
geo_ontology
:
begin sem_rdfctx.create_policy (policy_name => 'SEM_EXTR_PLUS_GEOONT', base_policy => 'SEM_EXTR', user_models => SEM_MODELS ('geo_ontology')); end; /
You can use an extractor policy to create one or more semantic indexes on columns that store unstructured documents, as explained in Semantically Indexing Documents.
Parent topic: Semantic Indexing for Documents