Assigning an Appropriate Meaning to Database Logic With Negation
Jeffrey David Ullman · 1994
Deductive database systems --- that is, database systems with a query language based on logical rules --- must allow negated subgoals in rules to express an adequate range of queries. Adherence to classical deductive logic rarely offers the intuitively correct meaning of the rules. Thus, a variety of approaches to defining the "right" meaning of such rules have been developed. In this paper we survey the principal approaches, including stratified negation, well-founded negation, stable-model semantics, and modularly stratified semantics. 1. Motivation Database query languages based on logic in some form are a promising trend in the development of modern database systems. Building on SQL, a language whose logical nature is hidden by the syntax, logical query languages preserve the declarative "say what you want, not how to get it" nature of SQL, while extending the expressiveness of the language beyond what SQL provides. See Ramakrishnan and Ullman [1993] for a survey of languages and...