Real time process algebra

We describe an axiom system ACP _p that incorporates real timed actions. Many examples are provided in order to explain the intuitive contents of the notation. ACP _p is a generalisation of ACP. This implies that some of the axioms have to be relaxed and that ACP can be recovered as a special case from it. The purpose of ACP _p is to serve as a specification language for real time systems. The axioms of ACP _p explain its operational meaning in an algebraic form.     

Revisiting timing in process algebra

We shortly review the framework of process algebras with timing presented by Baeten and Middelburg [Handbook of Process Algebra, Elsevier, 2001, Chapter 10]. In order to cover processes that are capable of performing certain actions at all points in some time interval, we add integration to the process algebra with continuous relative timing from this framework. This extension happens to reveal some points that are peculiar to relative timing. We go into these points. The most flagrant point is that, unlike in case of absolute timing, discretization cannot be added to the extension without first adding a mechanism for parametric timing like initial abstraction.     

Discrete time process algebra

The axiom system ACP of [BeK84a] was extended with real time features in [BaB91]. Here we proceed to define a discrete time extension of ACP, along the lines of ATP [NiS94]. We present versions based on relative timing and on absolute timing. Both approaches are integrated using parametric timing. The time free ACP theory is embedded in the discrete time theory.     

Real space process algebra

The real time process algebra of Baeten and Bergstra [Formal Aspects of Computing,3, 142–188 (1991)] is extended to real space by requiring the presence of spatial coordinates for each atomic action, in addition to the required temporal attribute. It is found that asynchronous communication cannot easily be avoided. Based on the state operators of Baeten and Bergstra [Information and Computation,78, 205–245 (1988)] and following Bergstra et al. [Proc. Seminar on Concurrency, LNCS 197, Springer, 1985, pp. 76–95], asychronous communication mechanisms are introduced as an additional feature of real space process algebra. The overall emphasis is on the introductory explanation of the features of real space process algebra, and characteristic examples are given for each of these.     

Modelling parallel databases with process algebra

With the current interest in using parallel computers as database servers to provide a scaleable parallel application which satisfies a real commercial need, there is a corresponding interest in performance prediction of parallel database systems. Both analytical and simulation approaches have been used and reported in the literature. This paper reports on an investigation into how a stochastic extension to classical process algebra (performance evaluation process algebra, PEPA) may be used for this purpose. This paradigm has a small but powerful set of elements which offers great flexibility for performance modelling. The paper describes how the approach has been adapted to handle database models, including the development of a technique, the decompositional approach, to handle the state-space explosion of parallel database models. It concludes with a comparison between the results obtained using this approach and those obtained using a different analytical approach.     

Process algebra with guards: Combining Hoare logic with process algebra

We extend process algebra with guards, comparable to the guards in guarded commands or conditions in common programming constructs such as if — then — else — fi and while — do — od.The extended language is provided with an operational semantics based on transitions between pairs of a process and a (data-)state. The data-states are given by a data environment that also defines in which data-states guards hold and how atomic actions (non-deterministically) transform these states. The operational semantics is studied modulo strong bisimulation equivalence. For basic process algebra (without operators for parallelism) we present a small axiom system that is complete with respect to a general class of data environments. Given a particular data environmentL we add three axioms to this system, which is then again complete, provided weakest preconditions are expressible andL is sufficiently deterministic.Then we study process algebra with parallelism and guards. A two phase-calculus is provided that makes it possible to prove identities between parallel processes. Also this calculus is complete. In the last section we show that partial correctness formulas can easily be expressed in this setting. We use process algebra with guards to prove the soundness of a Hoare logic for linear processes by translating proofs in Hoare logic into proofs in process algebra.Supported by ESPRIT Basic Research Action no. 3006 (CONCUR) and by RACE project no. 1046 (SPECS).Supported by RACE project no. 1046 (SPECS).     

Real time average and variance with modulo arithmetic

The arithmetic mean, and sample variance, are the most common summary statistics of a data set. There are circumstances (within computational loops, and in real-time data analysis, for examples) where it is desirable to maintain a current estimate of the mean and variance. The “lossy” (sometimes called the “running”) mean and variance are frequently useful also. We present an algorithm for these applications, and show the provisions necessary for use with cyclical (e.g. phase-angle) data.     

A real time process management system using RFID data mining

Recently, there have been numerous efforts to fuse the latest Radio Frequency Identification (RFID) technology with the Enterprise Information System (EIS). However, in most cases these attempts are centered mainly on the simultaneous multiple reading capability of RFID technology, and thus neglect the management of massive data generated from the RFID reader. As a result, it is difficult to obtain flow information for RFID data mining related to real time process control. In this paper, we propose an advanced process management method, called ‘Procedure Tree’ (PT), for RFID data mining. Using the suggested PT, we are able to manage massive RFID data effectively, and perform real time process management efficiently. Then we evaluate the efficiency of the proposed method, after applying it to a real time process control system connected to the RFID-based EIS. For the verification of the suggested system, we collect an enormous amount of data in the Enterprise Resource Planning (ERP) database, analyze characteristics of the collected data, and then compute the elapsed time on each stage in process control. The suggested system was able to perform what the traditional RFID-based process control systems failed to do, such as predicting and tracking of real time process and inventory control.     

实时数据驱动对象模型的方法及实现

在简单介绍了实时数据驱动的对象模型的总体框架后,主要分析讨论了在利用计算机语言构建逼真的三维对象整体外观以及使其内部结构可视化后,利用传感器对真实对象关键数据进行采集,通过网络传输,将采集到的数据加载到计算机虚拟的三维模型并对三维模型进行实时驱动,达到真实再现所模拟对象的内部结构的运行状况、当前位置姿态,以及传动过程的目的,以此对真实对象进行研究、分析与监测.文中最后以实例论证了这种方法的可行性、应注意的细节问题,并阐述了这种方法的具体意义.     

Delay‐dependent conditions for finite time stability of linear time‐varying systems with delay

This paper investigates the problem of finite time stability of linear time‐varying system with delay. By constructing an augmented time‐varying Lyapunov functional and using the Wirtinger‐type inequality deductively, delay‐dependent finite time stability conditions are derived and presented in terms of differential linear matrix inequalities (DLMIs). Then, the DLMIs are transformed into a series of recursive linear matrix inequalities (RLMIs) by discretizing the time interval into equally spaced time distances, and an algorithm is given to solve the RLMIs. Examples illustrate the feasibility and effectiveness of the proposed method.     

H ∞ model reduction for discrete‐time positive systems with inhomogeneous initial conditions

This paper addresses the H _∞ model reduction problem of discrete‐time positive linear systems with inhomogeneous initial conditions. For an asymptotically stable positive system with non‐zero initial condition, our goal is to approximate it by a reduced‐order initial‐valued positive system without introducing significant error. We establish a necessary and sufficient condition for the existence of a desired reduced‐order model such that the output error between the original system and the reduced‐order one is bounded by a weighted sum of the magnitude of the input and that of the initial condition. Moreover, based on congruent transformation and the dual form of bounded real lemma, several equivalent conditions are derived in terms of LMIs and an iterative convex optimization algorithm is developed accordingly. Finally, an illustrative example is presented to show the effectiveness of the proposed methods. Copyright © 2013 John Wiley & Sons, Ltd.