Information systems theoretical foundations

Some basic concepts concerning information systems are defined and investigated. With every information system a query language is associated and its syntax and semantics is formally defined. Some elementary properties of the query language are stated. The presented approach leads to a new information systems organization. The presented idea was implemented and the implementation shows many advantages compared with other methods. UVTRODUCTION This paper reports part of the activities of the Information Systems Group in Warsaw. We proposed and investigated in this Group a certain mathematical model for attribute based information systems. This model was first published by Pawlak[l] and extended by Marek and Pawlak[2]. In this report we use somewhat a new formulation of the discussed model and state some new problems. The idea of an information system investigated in this report is slightly related to that of Codd [3], Salton[4] and Wang and Chiang[S], however there are essential differences between them. In our approach in contrary to [4] and [5] the query language is formally introduced and extensively investigated. The language plays also an essential role in the approach of Cherniavsky and Schneiderl61, where not the data model but a data information language (extended first order language) is the departure point of an information systems study and implementation. In our approach we try link both mentioned views together. Formal definition of syntax and semantics of a query language is introduced in this approach-which offers deeper insight and understanding of phenomena involved in information processing, and provide facilities for using standard logical methods in this area. For example in the relational model, the query language is not defined precisely, there is no formal definition of the semantics what causes that some basic notions are obscure in this approach. The functional dependency of attributes is another good example to trace the differences between our approach and relational model. In both models data are arranged into tables. The columns are marked by attributes , and each column contains values of an attribute marking that column. Each such a table defines also all functional dependencies between attributes and this fact is a departure point of our definition of functional dependency, whereas in relational model some initial functional dependencies are assumed to be valid-independently from the database-on the basis of the knowledge about the real world. This may, however, lead to contradiction, that is to say, preassumed dependencies may be not consistant with …