Lehrgebiet Informationssysteme

FB Informatik

LG IS

AG DBIS

(C) AG DBIS

A Framework for Version-based Cooperation Control

W. Käfer

University of Kaiserslautern
P.O. Box 3049, 67653 Kaiserslautern, Germany
e-mail: haerder@informatik.uni-kl.de

Full paper (postscript version compressed by gzip)

Abstract:

In engineering environments the support of teamwork is a basic feature which is often not addressed by the design of so-called non-standard database systems (NDBS). First attempts to support cooperation were made by the definition of nested transactions, design transactions, etc. which modify the transaction's inherent ACID-principle. Ob servance of the ACID-principle guarantees the logical single user mode and isolation which encapsulates the work of the various users: this mode is the contrary of team work and cooperation, i.e. the designers of one team work in parallel, use unreliable data and they are aware of both these facts. Thus, we need a system which controls the cooperation by keeping track of data dependencies, rather than a system simulat ing single user mode. The use of unreliable data (belonging to one design object) is forced by the long du ration of design processes. Accordingly, the objects have to be made accessible at spe cial design states leading to versions of the objects, which provide different features based on their design state. These features are in general a subset of the features which should be provided by the final design object. Introducing these features (and means to detect and control them) into the DBMS gives us a notion of consistency in terms of correctness or completeness of design objects, i.e. a design object is consistent if it contains at least one version which provides all features specified as the design goal. Furthermore, each subset of the features itemizes a distinct level of consistency. Therefore, cooperation takes place by providing and using object versions along with their features, i.e. at different consistency levels. Hence, cooperation control can be focused on controlling object versions and usage relations among them. Thereby, obeying the consistency levels which are provided and which are demanded. Using these consistency levels for conflict detection and resolution leads to meaningful co operation control. In this paper we introduce a version model as basis for the support of teamwork. Ver sions comprise the data belonging to one (complex) design object valid at a particular design state. Furthermore, we introduce the notion of feature sets which we use as a means to detect, achieve, and control the consistency of object versions. We demon strate which functionality has to be added to the database management system in order to support cooperation.

Published in Proc. 2nd Int. Symposium on Database Systems for Advanced Applications (DASFAA), Tokyo, Japan, 1991.