Efficient Reasoning with Rules and Ontologies.

ERRO is an FCT-funded project (PTDC/EIA-CCO/121823/2010) aimed at addressing the problem of effectively and efficiently reason with knowledge available on the Semantic Web, integrating ontological knowledge and deductive rules.

Conceived within the Semantic Web context, ERRO builds upon three important observations:

1. Ontologies are necessary and useful for knowledge representation and the formalisms developed, e.g. OWL, are powerful enough to capture existing modelling languages used in software engineering.
2. Rules are fundamental to overcome the limitations found in OWL and provide constructs that are more natural for software developers (e.g. Closed World Assumption as used in databases).
3. New knowledge-based systems are not isolated and need mechanisms to act, reason, and evolve in the Semantic Web environment.

ERRO contributed with theoretical developments and state-of-the-art tools to effectively and efficiently address two main problems:

1. querying and updating (possibly inconsistent) knowledge bases tightly integrating ontologies and reasoning rules originating from a diversity of sources
2. event monitoring to automate the execution of active rules

ERRO's resulting theoretical developments constitute, on their own, an advancement of the state-of-the-art in knowledge representation and reasoning. ERRO's tools open up the ground for a new class of knowledge-rich applications that support dynamic data and application integration, automation and interoperation of business processes and problem-solving in various domains, while enforcing correctness of behaviour and allowing to trace the knowledge used and decisions taken.

Some of ERRO's highlights include:

1. Development of semantics and proof procedures for (possibly inconsistent) hybrid knowledge bases composed of non-monotonic rules and description logic ontologies, both for the general case, as well as for specific application-oriented tractable fragments (e.g. ontologies based on the OWL 2 EL and QL profiles).
2. Development of a unifying theory for updates of knowledge bases encompassing both non-monotonic rules and description logic ontologies, following our novel insights into the problem of developing semantic update operators for non-monotonic rule bases.
3. Development of modular hybrid update operators for important application-oriented fragments of hybrid knowledge bases.
4. Implementation and release under Public License of NoHR (Nova Hybrid Reasoner), a plug-in for the ontology editor Protégé that allows its users to query (possibly inconsistent) knowledge bases composed of both an ontology in OWL 2 EL or QL and a set of reasoning rules.