Richard St-Denis

Planning control rules for reactive agents

Abstract A traditional approach for planning is to evaluate goal statements over state trajectories modeling predicted behaviors of an agent. This paper describes a powerful extension of this approach for handling complex goals for reactive agents. We describe goals by using a modal temporal logic that can express quite complex time, safety, and liveness constraints. Our method is based on an incremental planner algorithm that generates a reactive plan by computing a sequence of partially satisfactory reactive plans converging to a completely satisfactory one. Partial satisfaction means that an agent controlled by the plan accomplishes its goal only for some environment events. Complete satisfaction means that the agent accomplishes its goal whatever environment events occur during the execution of the plan. As such, our planner can be stopped at any time to yield a useful plan. An implemented prototype is used to evaluate our planner on empirical problems.

EB3: an entity-based black-box specification method for information systems

This paper describes a formal method for specifying the observable (external) behavior of information systems using a process algebra and input-output traces. Its notation is mainly based on the entity concept, borrowed from the Jackson System Development method, and integrated with the requirements class diagram to represent data structures and associations. The specification process promotes modular and incremental description of the behavior of each entity through process abstraction, entity type patterns, and entity attribute function patterns. Valid system input traces result from the composition of entity traces by using parallel composition operations. The association between input traces and outputs through an input-output relation completes the specification process.

μcROSE: automated measurement of COSMIC-FFP for Rational Rose RealTime

Abstract During the last 10 years, many organizations have invested resources and energy in order to be rated at the highest level as possible according to some maturity models for software development. Since measures play an important role in these models, it is essential that CASE tools offer facilities to automatically measure the sizes of various documents produced using them. This paper introduces a tool, called μcROSE, that automatically measures the functional software size, as defined by the COSMIC-FFP method, for Rational Rose RealTime models. μ c ROSE streamlines the measurement process, ensuring repeatability and consistency in measurement while reducing measurement cost. It is the first tool to address automatic measurement of COSMIC-FFP and it can be integrated into the Rational Rose RealTime toolset.

Extending statecharts with process algebra operators

This paper describes an adaptation of statecharts to take advantage of process algebra operators like those found in CSP and EB3. The resulting notation is called algebraic state transition diagrams (ASTDs). The process algebra operators considered include sequence, iteration, parallel composition, and quantified synchronization. Quantification is one of the salient features of ASTDs, because it provides a powerful mechanism to precisely and explicitly define cardinalities in a dynamic model. The formal semantics of ASTDs is expressed using the operational style typically used in process algebras. The target application domain is the specification and implementation of information systems.

Synthesis of Controllers of Processes Modeled as ColoredPetri Nets

This paper presents an adaptation of a supervisory control theory and a supervisor synthesis problem to a class of colored Petri nets. More specifically, the forbidden state control problem with full observation, in which a discrete-event system is modeled as a colored Petri net with a symmetry specification, is investigated. This problem is decidable if the colored Petri net has finite color sets and bounded places. A new algorithm for deriving a controller is presented in detail with a proof of correctness. Unlike conventional algorithms that explore the entire reachable set of states, our algorithm avoids an exhaustive search of the state space by exploiting a symmetry specification. It performs particularly well when applied to large but structured processes with similar components. Furthermore, this approach leads to a representation of controllers which are smaller than those obtained with automaton-based approaches.

Control of Parameterized Discrete Event Systems

This paper investigates the control of parameterized discrete event systems when specifications are given in terms of predicates and satisfy a similarity assumption. This study is motivated by a weakness in current synthesis methods that do not scale well to huge systems. For systems consisting of similar processes under total or partial observation, conditions are given to deduce properties of a system of n processes (arbitrary size) from properties of a system of n0 processes (bounded size), with n ≥ n0. Furthermore, it is shown how to infer a control policy for the former from the latter’s, while taking into account interconnections between processes.

Linear flowchart generator for a structured language

This article refers to a paper by Nassi and Shneiderman published in this review [1]. They introduced a type of flowchart specially designed for structured programming. We have defined a similar flowchart language for the PASCAL programming language [2, 3] and designed a program which, given a program written in PASCAL, generates the corresponding flowchart. The article presents a description of the output produced by this flowchart generator.

Web technologies in support of virtual manufacturing environments

The development of distributed architectures and server-side component model for pervasive and safety-critical client-side manufacturing applications represents a very exciting challenge, particularly when the World Wide Web is used as a standard platform. On one hand, the component-based paradigm promises to enable software application development, integration, and deployment through assembly and distribution among decentralized servers across networks. On the other hand, the latest Web-based technologies, such as Web services, XML-based standards, and dynamic Web pages, provide powerful tools to enhance the overall efficiency of monitoring, operation, and control tasks for supporting smooth cross-organizational logistic manufacturing processes. This paper explores some of these recent technologies through the presentation of an experiment conducted with the aim of eventually realizing complex virtual manufacturing environments.

An Efficient Algorithm for Controller Synthesis under Full Observation

This paper presents a simple and flexible on-line synthesis algorithm that derives the optimal controller for a given environment. It consists of finding the greatest possible number of admissible event sequences of a discrete-event system with respect to a requirements specification. It generates and explores the state space on-the-fly and uses a control-directed backtracking technique. Compared to a previous algorithm of Wonham and Ramadge, our algorithm does not require explicit storage of the entire work space and backtracks on paths of arbitrary length to prune the search space more efficiently. This paper also discusses an implementation of our algorithm and includes an evaluation of its performance on a variety of problems.

Component-Based Method for the Modeling and Control of Modular Production Systems

Control software systems for manufacturing plants reveal common system architectural elements. This suggests taking advantage of a development paradigm based on reusable components. Creating and upgrading a repository of reusable components suitable for many systems that share common characteristics present a challenge for engineers, especially if composition mechanisms must be founded on control theories of discrete event systems and if formal synthesis tools must be integrated into well-accepted component-based software development processes. This paper explores a component model and a pragmatic method for the development of control software systems. The method, along with the underlying component model, fills the gap between a hierarchical control theory and component-based software engineering. A detailed case study developed around a Festo didactic learning modular production system demonstrates the relevance of the proposed approach to industrial application.