| In today's business world, large quantity of data is usually stored in the database format for processing. In recent years, Knowledge Base (KB) represented in the ontology format has been developed as an alternative way to store data. However, the common validation operation applied to KB does not always perform as expected from a closed-world perspective. Knowledge Base typically is supposed to represent an "open-world". For the relational database theory, the database domain is always a "closed-world". This difference is often referred to as "open-world" vs. "closed-world". Most common Description Logic (DL) reasoners assume a KB is in open-world when performing reasoning tasks on it. The results from these reasoning tasks do not always satisfy the users who view the KB with a database perspective which typically is closed-world. In this thesis, we propose an approach validating a KB under the closed-world semantics. We design and implement a DL ontology reasoner prototype which is capable of dealing with both open-world reasoning tasks and closed-world reasoning tasks. Reasoning with a KB that is partially closed using the 'K' operator is also discussed in this thesis. Traditional database users will have a flexible way to express that some parts of the KB are open and some are closed by using K-operator reasoning services. |
