Toshikazu Kawamura

Evaluation of object-oriented database for distribution network monitoring system

This paper outlines an original object-oriented database management system which is designed for industrial applications and describes results of an experiment to apply it to a graphical user interface in a power distribution monitoring system. Database management systems are widely used and achieve high productivity and high reliability of data management in the business field and in some engineering areas. However conventional database systems, especially relational database systems, are rarely used in industrial real-time fields. This paper presents advantages of object-oriented concepts for modeling complex data of a monitoring system. The object-oriented database successfully supports data-modeling requirements of GUI applications, and the performance is well acceptable for GUI applications.

Object-oriented database management system for process control systems—development and evaluation

This paper presents an object-oriented database management system designed for industrial applications, and describes experimental results in applying it to a power supervisory control system. Database management systems achieve high productivity and high reliability of data management in the business field and in some engineering areas and are widely used. However, conventional database systems, especially relational database systems, are rarely used in industrial real-time fields. For example, power supervisory control systems require a high performance database system which uses a complex data structure. In such systems database systems must be able to retrieve and up date information within a limited time (e.g. less than 166 msec). It is difficult for relational database systems to manage complex data structures and to achieve the performance needed for real-time process control. We have developed a compact and high performance object-oriented database system “Odb” for process control systems. We propose a data model which integrates a set of objects which belongs to the c!ass and a set defined by the user. We have also developed an architecture which provides uniform access to persistent objects and transient objects, and an efficient implementation method. We present the data model, the database language and the architecture of Odb, then show advantages of object-oriented database systems applied in power supervisory control systems. Permission to make digital or bard copia of ail 01 prrt of Ihis Wok for persod or classroom use is gruacd without fee provided tht copies are not made or distributed fa prolii oc COIN’II~~ advantage and that copies bear this notice and the full citalion in the first page. To copy othcrwisc, to republish, to posl on scrws 0~ to redistribute to lists. requira prior specific pcnnissian ~MUW a fee. SAC 9, San Antonio. Texas 01998 ACM I-581 13-086-4/99/0001 S5.00 INTRODUCTION Computer systems for plant supervisory control must be reliable and react responsively. Database management systems are widely used and achieve high pm ductivity and high reliability of data management in the business field and in some engineering areas. However conventional database systems, especially rels tional database systems, are rarely used in industrial real-time fields. Conventional database technology has some shortcomings as follows [2, S]: l The data model is too simple for modeling complex nested entities. l Data types are limited. 0 Semantic concepts are lacking. l The response of relational database ss&ems is unacceptable for real-time systems. l Database languages (SQL) are very d&rent from programming languages, in both data model and data structures. This problem is known as impedance mismatch. Many commercial object-oriented database management systems (OODB) are available now. However, most of them have a lot of unnecessary features and can not easily achieve the response needed for real-time process control. Compact and responsive OODB are required in the field of industrial systems. Therefore, we developed “Odb” with the following features for real-time protest control applications. (1) Support of object-oriented concepts (2) Quick response and high performance (3) NO impedance mismatch In the next section, we present the data model, the database language and the architecture of Odb. The third section shows advantages of object-oriented database systems applied in power supervisory control systems. The results presented in the fourth section. OBJECT-ORIENTED DATABASE Odb This section describes the functional specification of Odb. Odb has the following features [4]. (1) Support of object-oriented concepts Odb supports all object-oriented concepts, such as Encapsulation, Classes, Inheritance, Polymorphism and Overloading. It also provides extent[3] and built-in Collection (Set and Bag). The extent is the set of all instances of a class and the Collection is a set of objects specified by a user. (2) Quick response and high performance Odb is a compact and efficient database system that has adopted the client/server architecture. The Odb database engine adopts pointer swizzling at page fault time technique to translate the object identifier of an object to virtual addresses. Furthermore, Odb provides clustering. indexing and client cache mechanisms. (3) No impedance mismatch To achieve high productivity, Odb provides C++ based data-base language, The user can define a database schema as a class definition, and can make, store, and retrieve persistent objects in the same way as non-persistent objects in C++. Odb is designed for real-time use. Therefore, we simplified the functions which commercial OODB supports and attempted to produce high performance by using a concise functional specification.