Inevitability in diamond-discrete systems

Abstracts

pleteness. A subset of basic ER-diagram transformations is shown to be ERD-complete, while the whole set of the ER-diagram transformations is shown to be vertex-complete. Authors' Abstract

V.M. Markowitz and J.A. Makowsky: Incremental Reorganization of Relational Databases, Department of Computer Science, Israel Institute of Technology, Haifa, Feb. 1987. The evolution of an information system is reflected in data modeling by database reorganization. Database reorganization consists of schema restructuring coupled with entity-conservative state modificat/~r. Since algebraic operations consist of the embedding of schema restructuring and state modification, relational database reorganization has been mostly centered on relational algebra. This approach fails to capture the information structure aspects of the database reorgan~ation, mainly because the traditional relational model does not provide a suitable framework to deal with information. Entity-Relationship(ER) consistency expresses the capability of relational databases to model information oriented systems. A relational schema consisting of relational schemes, together with key and inclusion dependencies, is said to be ER-consistent if it complies with an entity-relationship structure, meaning that it is representable by an Entity-Relationship diagram. For ER-consistent databases both the schema restructuring and the state modification are more complex than for traditional relational databases. The basic relational schema restructuring manipulations are the addition and removal of relation schemes, accompanied by the modification of the inner and inter-relation dependencies. Recently we have defined a set of incremental and reversible schema restructuring manipulations as the translates of a set of vertex-oriented ER-diagram transformations. In the present paper we deal with the second component of database reorganization, namely entity-conservative state modifications that keep invariant the set of entities in the database, and the reorganization operations as a whole. We introduce two operations that perform incremental, that is, propagation-free and single-relation, conservative state modifications. We prove that these

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operations form a complete, in a relational-calculus base sense, set. Database reorganization operations are defined as consisting of compatible pairs of incremental restructuring and conservative state modifica:ion manil:t~.lations. The proposed set of database reorganization operations is shown to be complete. Authors' Abstract

Andrzej Matuszewski: Frequentist interpretation of Bayes confidence regions and binomial Scheme, Institute of Computer Science, Polish Academy of Sciences, Warsaw, Jan. 1987. A notion of Bayesian frequentist interpretation of confidence regions is introduced. Since the relation of this interpretation with confidence coefficient of bayesian regions is established it seems that the practical importance of these regions grows. The consequence for the problem of confidence interval for the parameter of binomial scheme are described. Particularly a new computational procedure for the small sample situation is proposed. Author's Abstract

Wojciech Penczek: Inevitability in diamond-discrete systems, Institute of Computer Science, Polish Academy of Sciences, Warsaw, Jan. 1987. A general definition for inevitable properties in discrete concurrent systems with a diamond property is proposed. Equivalence to Mazurkiewicz's definition is proved. A partial order framework is considered. Author's Abstract

R.M. Roth and G. Seroussi: Encoding and Decoding of BCH Codes Using Light and Short Codewords, Department of Computer Science, Israel Institute of Technology, Haifa, Jan. 1987. It is shown that every q-ary primitive BCH code of designed distance 8 and sufficiently large length n contains a codeword Co of weigi~t w = O(8), and degree deg(c 0) = o(n). Thes¢ so called fight and short codewords are used to describe encoding and decoding algorithms which rn on