Jan 1, 1967
This report continues the work, begun in RM-5428, of developing and implementing a theory of data retrieval for a computerized question-answering system in which the queries are represented as formulas of the predicate calculus and the database consists of atomic sentences. Algorithms for processing queries involving a full vocabulary of binary operators are given. It is shown that definite formulas having at most two levels of operators from certain minimal operator sets can always be transformed into proper formulas (i.e., formulas consisting entirely of definite subformulas) and algorithms for these "admissibility" transformations are given. In addition to the conventional operators, a new form of universal quantification is proposed for query systems. Rules for evaluation are given, and it is shown that the class of definite formulas is closed under this new "generalized universal quantification." Finally, theoretical limitations on methods of determining propriety through admissibility transformations are discussed.