  An algorithm for answering conjunctive queries over SHIQ knowledge bases that
is coNP in data complexity is given. The algorithm is based on the tableau
algorithm for reasoning with individuals in SHIQ. The blocking conditions of
the tableau are weakened in such a way that the set of models the modified
algorithm yields suffices to check query entailment. The modified blocking
conditions are based on the ones proposed by Levy and Rousset for reasoning
with Horn Rules in the description logic ALCNR.

Logic in Computer Science;Artificial Intelligence;Computational Complexity