What is "materialization"? Materialization always means that OntoBroker evaluates rules in advance (on startup) and stores the results in the extensional database (EDB). This has the following effects:
|•||Queries can be executed very fast (as OntoBroker has fewer rules to evaluate).|
|•||OntoBroker needs more memory (as all facts defined implicitly by rules are stored in the database).|
|•||The startup time increases (sometimes significantly because all of the reasoning is done in the startup phase).|
So to keep it short: Materialization is a very good way to optimize performance and to provide guaranteed answering times. Another important use case for materialization is to materialize database mapping rules. This way the users of the ontology can execute offline queries (without access to the mapped database).
NOTE: Materialization is only supported for the ontology langugages ObjectLogic and RDF. Currently OWL ontologies cannot be materialized.