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Computing Methodologies


We consider the problem of answering queries against a knowledge base (KB) using secrets, whenever it is possible to do so without compromising secrets. We study query answering against EL knowledge bases. We provide a polynomial time algorithm that, given an EL KB Sigma, a set S of secrets to be protected and a query q or the form C(a) or r(a,b), outputs ``Yes'' whenever Sigma entails q and the answer to q, together with the answers to any previous queries answered by the KB, does not allow the querying agent to deduce any of the secrets in S. This approach allows more flexible information sharing than is possible with traditional access control mechanisms.