The computational complexity of a number of problems relating to minimal models of non-Horn deductive databases is considered. In particular, the problem of determining minimal model membership is shown to be NP complete for non-recursive propositional databases. The structure of minimal models is also examined using the notion of a cyclic tree, and methods of determining minimal model membersh...

In this paper formal properties of CI in diierent frameworks are studied. The rst part is devoted to the comparison of three diierent frameworks for study CI: probability theory, theory of relational databases and Spohn's theory of ordinal conditional functions. Although CI{models arising in these frameworks are very similar (they satisfy semigraphoid axioms) we give examples showing that their...

This paper, the first step to connect relational databases with systems consequence (Kent [5]), is concerned with the semantics of relational databases. It aims to to study system consequence in the logical/semantic system of relational databases. The paper, which was inspired by and which extends a recent set of papers on the theory of relational database systems (Spivak [6] [7]), is linked wi...

For a given set of queries (which are expressions in some query language) Q = {Q1, Q2, . . . Qk} and for another query Q0 we say that Q determines Q0 if – informally speaking – for every database D, the information contained in the views Q(D) is sufficient to compute Q0(D). Query Determinacy Problem is the problem of deciding, for given Q and Q0, whether Q determines Q0. Many versions of this p...

Bhavani Thuraisingham is a lead engineer with the MITRE Corporation where she has initiated R & D activities in secure distributed database systems, secure object-oriented database systems, and secure intelligent database systems. She is currently working on multilevel object-oriented data models, approaches to handle the inference problem, theory of concurrency control for multilevel databases...

Structured Query Language (SQL) is the dominant language for querying relational databases today, and is an essential topic in introductory database courses in higher education. Even though the language is syntactically simple, relatively concise, and highly structured, students experience many difficulties while learning to express queries in SQL. In recent years a small number of software too...

Correctness verification of query results is a significant challenge in database outsourcing. Most of the proposed approaches impose high overhead, which makes them impractical in real scenarios. Probabilistic approaches are proposed in order to reduce the computation overhead pertaining to the verification process. In this paper, we use the notion of trust as the basis of our probabilistic app...

The database model presented in this paper is suitable for application in which queries may require non-crisp references to certain attributes. The data item (attribute) values may be crisp or fuzzy. For instance, such adjectives as 'high' or 'normal' may be attribute values for the attribute blood pressure. A disease or a condition can be described by a number of symptoms which may be crisp al...

It seems that designing and implementing database engines may have become a lost art. Although most standard database text books [1] [2] [3] include ample coverage of algorithms for design and implementation database engines, many computer science programs seem to provide minimal coverage of file organizations, theoretical foundations, and algorithms necessary to build a database engine. The sy...