It is well-known that there are circumstances where applying Reiter s closed world assump- tion (CWA) will lead to logical inconsistencies . In this paper, a new characterization of the CWA consistency is pesented and an algorithm is proposed for determining whether a datalase with- out function symbols is consistent with the CWA. The algorithm is shown to be efficient.

Up to now, no satisfactory theory has been established for formalizing incomplete knowledge in incomplete databases. In this paper, we clarify why existing closed world approaches, such as the CWA, the GCWA, the ECWA, circumscription, predicate completion and the PWA, fail to do so, and propose a new method. The method is an augmentation of both the ECWA and circumscrip- tion with the mechanism to discriminate implicitly expressed positive knowledge, negative knowledge and truly unknown knowledge.

A complex object is an abstraction and description of a complex entity of the real world. Many applications in such domains as CIMS, CAD and OA define and manipulate a complex object as a single unit. In this paper, a definition of the model of complex objects is given, and the concurrency control mechanism of complex objects in WHYMX object-oriented database system is described.

The data model of WHYMX complicates transaction management. Traditional locking method is not powerful enough to solve the new problem of concurrency control of WHYMX s transaction. This paper presents a number of concurrency control algorithms based on the extended locking method.

In order to reduce the disk access time, a database can be stored on several simultaneously accessi- ble disks. In this paper, we are concerned with the dynamic d-attribute database allocation problem for range queries. An allocation method, called coordinate modulo allocation method, is proposed to al- locate data in a d-attribute database among disks so that the maximum disk accessing concurrency can be achieved for range queries. Our analysis and experiments show that the method achieves the optimum or n…

This paper formulates an architecture for information integration in computer integrated manufacturing systems (CIMS). The architecture takes the frame structure as single link among applica- tions and between applications and physical storage. All the advantages in form features based inte- grated systems can be found in the frame-based architecture as the frame structure here takes form fea- tures as its primitives. But other advantages, e.g., default knowledge and dynamic domain knowledge can be attached…

Two kinds of net operations, addition and Cartesian production of P/T nets, are introduced. They are defined on the set of underlying net of P/T systems. The conditions for preserving structural proper- ties of Petri net after these operations are discussed. It is shown that the set of P/T nets forms an Abelian group for net addition operation and the inverse net of a P/T net in usual meaning of net theo- ry is exactly the inverse of this P/T net as an element of the P/T net group; and that the set of P/T n…

This paper presents a kind of visual programming, which is called R-technology of programming. The R-technology is independent of any programming language or operating system and the R-chart is in accord with international standard (ISO 8631H). The package of R-technology has been applied to the high level languages such as PASCAL, C, ASSEMBLER, FORTRAN, PL/1, MODULA-2 and RTRAN. This package is applied to computers ranging from mainframes (IBM 370) and minis (VAX) to micros (IBM/PC).

Static optimization of logical queries is, in substance, to move selections down as far as possible in evaluating logical queries. This paper extends Ullman s RGG (Rule/Goal Graph) and introduces P- graph, with which a wide range of recursive logical queries can be statically optimized top-down and evaluated bottom-up, some of which are usually optimized by dynamic approaches. The paper also shows that for some logical queries the complexity of pushing selections down and computing bottom-up is related to t…

In this paper we generalize the while-rule in Hoare calculus to an infinite one and then present a sufficient condition much weaker than the expressiveness for Cook s relative completeness theorem with respect to our new axiomatic system. Using the extended Hoare calculus we can derive true Hoare formulas which contain while- statements free of loop invariants. It is also pointed out that the weak condition is a first order property and therefore provides a possible approach to the characterization of relat…

In the so called “Group Problem” (we would like to term it “Group-Consulting Type Cooperation”), ESs of the same cooperating group may have different views towards the same problem, and the differences may sometimes be very great. For the circumstance of those ESs with relatively closer views, we present in this paper three methods of consistency treatment and a method for calcula- ting the maximal deviation of the confidence value about the cooperating group s common view based on the consistency degree of…

The principal feature of nonstationary cellular automata (NCA) is that a local transition rule of each cell is changed at each time step depending on neighborhood configuration at previous time- step The identification problem for NCA is extraction of local transition rules and the establishment of mecha- nism for changing these rules using sequence of NCA configurations. We present serial and parallel algorithms for identification of NCA.