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Abstract-This paper presents a data model of a realtime object-oriented database. In addition to the logical consistency constraints, a real-time database must support both temporal aspects of data and timing constraints of transactions upon the data. The RTO-RTDB data model support these requirements by specifying objects that contains: time-constrained data; time-constrained methods; and concurrency control mechanisms.
Keywords: Data Model; Real-Time; Object Model; Database;
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1. Introduction
A Real-Time (RT) database is a database in which both the data and the transactions upon the data may have timing constraints. The mostly used data model for RT databases is the relational model [1]. However, due to the nature of many RT applications that must handle complex real world objects with short deadlines, many researchers believe that the object-oriented model is more natural and powerful than the relational model [2]. A RT database have all requirements of traditional databases, such as the management of accesses to structured, shared and permanent data, and they require management of time-constrained data and time-constrained transactions [3]. RTO-RTDB (Real-Time Object for Real- Time DataBases) is a RT object-oriented database model that incorporates these concepts [4].
The RTO-RTDB model is based upon an earlier model, called real-time object-oriented data model [5], on which it incorporates time-constrained data, time-constrained methods and concurrency control mechanisms. As shown in Figure 1, each RTO-RTDB object has four components: (i) a set of RT attributes, (ii) a set of RT methods, (iii) a mailbox, and (iv) a local controller.
This paper represents an extension of the RTO-RTDB data model. We have drawn from our experience in the design of RT databases [6] to identify the basic research issues involved in the design of RT object-oriented databases. The next section provides background information on RT databases. The third section surveys related work, and summarizes the features that are unique to RT databases. The fourth and the fifth sections introduce the RTO-RTDB object model. They present the native RTO-RTDB components introduced in [4] and advanced ones proposed in this paper, respectively. The last section concludes the paper and describes issues for future investigations.
2. Real-Time Databases
A RT database is a time-constrained database designed to handle not only transactions with timing constraints, but also data...