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|Title |Introduction |Integrating App's |Integrity Maintenance |AOODB Model |Backward Propagation |HVC |Constraint Maintenance |Conclusion |References|

Backward Propagation of User-Defined Integrity Constriant in Active Object-Oriented Database
since 24 June, 1996, last modified 24 June, 1996


Namchul Do 24 June, 1996

Abstract

This thesis proposes a framework of engineering constraint maintenance using an active object-oriented database and solves a problem encountered when implementing the framework. The framework is proposed for the information driven CIM system that integrates engineering constraints as well as data among various applications. It resolves problems of the existing application-oriented constraint maintenance, which scatters the constraints into heterogeneous applications, hence, incurs management of duplicated rules for constraints, implementation of dedicated constraint checking logic for heterogeneous applications, and additional translation of data for constraint checking. The proposed framework enables the applications to effectively access and manage the engineering constraints. It is possible due to the integrated management of constraints on a database using triggers, that is, on an "active" database. Further, object-orientation of the database allows expressing and manipulating complex engineering constraints by permitting methods in triggers.

Existing active object-oriented databases, however, cannot properly support certain constraints that are specified on a set of classes that form a class composition hierarchy. Those are the cases where the constraints must be maintained in the forward direction along the class composition hierarchy as well as in the backward direction. We call these kinds of problems "backward propagation problems" and investigate several approaches to resolve them using currently available techniques. Based on one of the approaches which uses virtual classes, a new constructor, called CONSTRAINTCCH is proposed to support integrity maintenance in a class composition hierarchy. It uses only resources from an active object-oriented database so that the applications may be integrated without additional facilities for constraint maintenance. Moreover, the virtual class in the backward propagation approach, which we call Horizontal Virtual Class, enables efficient representation and management of constraints, using participating objects' identifiers and methods for constraints.

Advantages of the proposed framework and the constructor for the backward propagation are demonstrated on a design constraint management system that supports a control panel design.

Table of CONTENTS

1 Introduction

1.1 Integrity Maintenance in Engineering Databases

1.2 Engineering Semantics Loss in CIM Environments

1.3 Scope and Goals of Research

2 A Framework for Integrating Engineering Applications

2.1 A Framework

2.2 Integrity Maintenance Approaches in Engineering Databases

3 Integrity Maintenance in Active Databases

3.1 Active Databases

3.2 Separation of Integrity Constraints from General Trigger/Event

3.3 Constraint Enforcement with Integrity Analysis

4 An Active Object-Oriented Data Model

4.1 An Object-Oriented Data Model

4.2 Virtual Classes

4.3 Triggers

4.4 Associative References

5 Backward Propagation

5.1 Problems in User Defined Integrity Constraint

5.2 Concept of The Backward Propagation

5.3 Backward Propagation Approaches

5.3.1 Backward Propagation with Method (Expression) Duplication

5.3.2 Backward Propagation with Method Call

5.3.3 Backward Propagation with Virtual Class

6 Horizontal Virtual Class

6.1 Comparisons of Three Backward Propagation Approaches

6.2 Characteristics of HVC

6.3 CONSTRAINTCCH

7 Constraint Management in an Engineering Design System

7.1 A Design Constraint Management System

7.1.1 Architecture 92

7.1.2 Schema of the Design Database and Its Extension

7.1.3 Verification and Management of Design Constraints

7.2 An Illustrative example : An Example of Control Panel Design

7.2.1 Design of A Control Panel

7.2.2 Product Definition

7.2.3 Constraints on Controls

7.2.4 Integration of Applications

8 Conclusion

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Korean Engineering Databases copyright Namchul Do, 1996