Titlebook: MFDBS 89; 2nd Symposium on Mat János Demetrovics,Bernhard Thalheim Conference proceedings 1989 Springer-Verlag Berlin Heidelberg 1989 Daten

hieroglyphic

Selective refutation of integrity constraints in deductive databases,se. We have applied such method to integrity constraint checking but it seems useful in other application areas as well..Despite to its simplicity in the case of definite goals and programs, when introducing negation problems arise. We restricted ourselves to definite programs and normal goals becau

周兴旺

Approaches to updates over weak instances,lem of updating databases through interfaces based on the weak instance model..Insertions and deletions of tuples are considered..It is possible to distinguish between semantic and heuristic, or computational, approaches. The two semantic approaches turn out to be very similar, even if they have dif

藕床生厌倦

Index selection in relational databases,es, updates, insertions and deletions, and we define a function that calculates the transactions total cost when an index set is used. Our aim was to minimize the function cost in order to identify the optimal set. The algorithms proposed in previous studies require an exponential time in the number

躺下残杀

Towards a schema design methodology for deductive databases,n the real world can simply and efficiently be obtained just by looking at its representation, i.e., just by querying the database. In this paper, we try to direct the reader‘s attention to the schema design problem for deductive (or logic oriented) databases. In order to provide a formal framework

倾听

Shared abstract data types: An algebraic methodology for their specification,hich it is possible to avoid the unnecessary constraints on concurrency usually imposed by traditional transaction management approaches. The used method is based on the definition of the data as abstract data types in the well known algebraic method. The semantics of the data is given in two steps:

GLOSS

monologue

Interaction of authorities and acquaintances in the DORIS privacy model of data, kinds of rights: Authorities on roles (allowing operations) which are statically declared for groups (classes), and acquaintances (access capabilities) that are dynamically granted to persons (instances). The interaction of authorities and acquaintances is studied and some pitfalls are identified.

无法取消

Logical rewritings for improving the evaluation of quantified queries,iple common to the methods that have been proposed for answering quantified queries. Relying on this concept, we define the class of . (cdi) formulas. We show that cdi queries can be constructively evaluated by searching only the relations they refer to. Therefore, cdi queries admit domain independe

暗语

伤心

An extended view on data base conceptual design,s into the research area a new side of the conceptual design process namely, structural knowledge acquirement; 2) Data Base conceptual design is seen as a process of synthesizing, at the level of the Universe, the structural knowledge acquired separetly from subuniverses. For this extended conceptua