Maria Ligia B. Perkusich

Object Oriented Real-Time Database Design and Hierarchical Control Systems

This paper discusses aspects related to the integration between Database Management Systems and Hierarchical Real-Time Control Systems. A method that can be applied to the design and prototyping of both realtime control systems and real-time databases is introduced. This method is based on an extension of High-level Petri nets, named G-Nets, allowing object oriented modeling and evolutionary systems development. An example based on a flexible manufacturing system is also presented.

Analysis of periodic transactions and semantic concurrency control for real-time databases using colored Petri nets

We deal with the analysis of semantic concurrency control as well as the scheduling of periodic transactions with hard deadlines for real-time databases (RTBD). A coloured Petri net based method as well as analytical techniques are adopted. The resulting model allows the behavioral analysis taking into account the semantic concurrency control for an effective RTDB application. Also, we define the valid schedules satisfying data and periodic transaction logical and temporal restrictions.

OBJECT ORIENTED DESIGN, MODULAR ANALYSIS, AND FAULT-TOLERANCE OF REAL-TIME CONTROL SOFTWARE SYSTEMS

When specifying, designing and analyzing complex real-time systems, it is necessary to adopt a modular or compositional methodology. This methodology shall allow the designer the ability to verify local properties of individual modules or components in the system, and also shall allow the verification of the correct behavior of interacting components. The application of Petri nets for the modeling and verification of systems, at specification and design levels are well known. Despite the powerful structuring mechanisms available in the Petri nets theory for the construction of the model of complex systems, the designer is still likely to face the problem of state explosion, when analyzing and verifying large systems. In this work we introduce a modular analysis methodology for a kind of high level Petri nets named G-Nets.

Formal specification of the epsilon serializibility considering quality of service

Recent research points to the real-time database systems (RTDB) as an integrant part in relation to applications as telephony, aviation and stock exchange online. Since for these activities it is not enough to keep the logical consistency of data and transaction, it is necessary to know the imposed temporal constraint to them. However, when some transactions are executed in concurrency way, the consistency of data and transactions cannot be guaranteed. Then, it is necessary that the system controls the interaction between them. The system that controls this interaction is called seriliazibility. In the RTDBs the serializibility is generalized to allow imprecision limited in the transaction processing. This imprecision is defined and controlled through the compatibility function (CF) aiming at allowing a large number of concurrent executions of the transactions. In this research we show a new approach for the CF. Thus, we insert quality of services (QoS) mechanisms in which these make possible that some parameters are limited to acceptable values in order to attend application intention.

A model in Petri Nets to analyze quality of service in real-time databases

In the last years it has been observed that real-time database systems (RTDB) are a key functional unit for the success of emergent applications with timing restrictions, such as electronic commerce, sensor networks, telephony systems and online trading. Due to the high service demand, many transactions may miss their deadlines. In the attempt to solve such problem, we present a RTDB model considering quality of service (QoS) to guarantee the performance. A simulation study, presented in this paper, shows that our model can achieve a significant improvement, in terms of deadlines miss and accumulated maximum imprecision resultant of the negotiation between the logical and temporal consistency. Furthermore, we show model analysis generated by the Design/CPN tool.