Reasoning about dynamically evolving process structures

We develop a Hoare-style proof system for reasoning about the behaviour of processes that interact via a dynamically evolving communication structure.     

Structure evolving systems and control in integrated design

Existing methods in Systems and Control deal predominantly with Fixed Systems, that have been designed in the past, and for which the control design has to be performed. The new paradigm of Structure Evolving Systems (SES), expresses a new form of system complexity where the components, interconnection topology, measurement-actuation schemes may not be fixed, the control scheme also may vary within the system-lifecycle and different views of the system of varying complexity may be required by the designer. Such systems emerge in many application domains and in the engineering context in problems such as integrated system design, integrated operations, re-engineering, lifecycle design issues, networks, etc. The paper focuses on the Integrated Engineering Design (IED), which is revealed as a typical structure evolution process that is strongly linked to Control Theory and Design type problems. It is shown, that the formation of the system, which is finally used for control design evolves during the earlier design stages and that process synthesis and overall instrumentation are critical stages of this evolutionary process that shapes the final system structure and thus the potential for control design. The paper aims at revealing the control theory context of the evolutionary mechanism in overall system design by defining a number of generic clusters of system structure evolution problems and by establishing links with existing areas of control theory. Different aspects of model evolution during the overall design are identified which include cases such as: (i) Time-dependent evolution of system models from “early” to “late” stages of design. (ii) Design stage-dependent evolution from conceptualisation to process synthesis and to overall instrumentation. (iii) Redesign of given systems and constrained system evolution. Within each cluster a number of well defined new Control Theory problems are introduced, which may be studied within the structural methodologies framework of Linear Systems. The problems posed have a general systems character, but the emphasis here is on Linear Systems; an overview of relevant results is given and links with existing research topics are established. The paper defines the Structural Control Theoretic context of an important family of complex systems emerging in engineering design and defines a new research agenda for structural methods of Control Theory. Copyright ©2002 IFAC     

A mathematical model of dynamically evolving economics

Cybernetics and Systems Analysis -     

Simulation of systems with dynamically varying model structure

Hybrid systems are dynamical systems composed of components with discrete and continuous behavior. Some systems change their structure during simulation, or their components behavior is essentially changing. This “structural dynamics” can be described in some modeling languages but the corresponding hybrid simulators have more or less restrictions in handling models with dynamically varying structure. Some basic approaches for the simulation of such systems are discussed in the context of modeling languages and simulators.     

Decentralized stabilization of dynamically interconnected systems

A decentralized stabilization design with most evenly distributed complexity of controllers is presented for dynamically interconnected systems.     

DECM,A User Oriented Formalism for High Level Discrete Event Specifications of Real-Time Systems

In this paper, we present DECM (Discrete Event Calculus Model), an original discrete event mathematical model for the specification of control systems at a high level of abstraction. Because the concept of event is more natural for nonspecialists than the concept of state, the proposed model is centered on the latter concept. This in turn permits the expression of asynchronous behavior without relying on the classical concept of state. In addition, DECM-based formalism offers an explicit representation of time that allows the use of timed simulations for the validation of formal specifications. This formalism is illustrated on a real-world industrial example.     

Incremental maintenance of semantic links in dynamically changing hypertext systems

One purported advantage of hypertext systems is the ability to move between semantically related parts of a document (or family of documents). If the document is undergoing frequent modification (for example while an author is writing a book or while a software design stored in the hypertext system is evolving) the question arises as to how to incrementally maintain semantic interconnections in the face of the modifications.

The paper presents an optimal technique for the incremental maintenance of such interconnections as a document evolves. The technique, based on theories of information retrieval based on lexical affinities and theories of incremental computation, updates semantic interconnections as nodes are checked into the hypertext system (either new or as a result of an edit). Because we use the semantic weight of lexical affinities to determine which affinities are meaningful in the global context of the document, introducing a new affinity or changing the weight of an existing affinity can potentially have an effect on any node in the system. The challenge met by our algorithm is to guarantee that despite this potentially arbitrary impact, we still update link information optimally.

Once established the semantic interconnections are used to allow the user to move from node to node based not on rigid connections but instead on dynamically determined semantic interrelationships among the nodes.     

Stochastic affine quadratic regulator with applications to tracking control of quantum systems

This paper deals with the regulator theory of stochastic affine systems. Applying a tensor formal power series method, stochastic bilinear quadratic regulator is solved numerically. An example about tracking control of quantum systems is given to show the usefulness of the developed theory.     

A formalization of geometric constraint systems and their decomposition

For more than a decade, the trend in geometric constraint systems solving has been to use a geometric decomposition/recombination approach. These methods are generally grounded on the invariance of systems under rigid motions. In order to decompose further, other invariance groups (e.g., scalings) have recently been considered. Geometric decomposition is grounded on the possibility to replace a solved subsystem with a smaller system called boundary. This article shows the central property that justifies decomposition, without assuming specific types of constraints or invariance groups. The exact nature of the boundary system is given. This formalization brings out the elements of a general and modular implementation.     

A preliminary investigation of information systems team structures

Productivity in the information age is widely perceived to be a major organizational problem. One strategy for enhancing organizational productivity has been the use of task teams. Assignment to task teams is usually based on individual technical expertise, individual availability, and/or positional politics rather than on the effectiveness of the team members in the specific organizational situation. This paper investigations characteristics of team members and then examines the effect of these characteristics and the requirements of the organizational task on team effectiveness.The findings indicate that the perceptual types of team members and the task structure impacts team effectiveness. It lends evidence that heterogeneity of perceptual types is best for solving unstructured tasks whereas heterogeneity can be counter-productive when solving structured tasks. It also suggests that one team might not be appropriate for all stages of a project. As the structure of the tasks change, the optimum team composition might also change.     

Robust output feedback stabilization of uncertain dynamic systems with bounded controllers

We propose a new class of infinitely many bounded output feedback controllers for uncertain dynamic systems with bounded uncertainties. No statistical information about the uncertainties is assumed. A variable structure systems approach is employed in the synthesis of the proposed output feedback controllers. The role of the system zeros in the output feedback stabilization using the variable structure approach is discussed. We show that the proposed controllers guarantee the practical stability of the closed-loop system and give estimates of the regions of practical stability.     

An iterative approach to verification of real-time systems

Verification of real-time systems is a complex problem, requiring construction of aregion automaton with a state space growing exponentially in the number of timing constraints and the sizes of constants in those constraints. However, some properties can be verified even when some quantitative timing information is abstracted. We propose a new verification procedure, where increasingly more complex abstractions of the region automaton are iteratively constructed. In many cases, the procedure can be stopped early, and thus can avoid the state space explosion problem.     

Sticker systems with complex structures

 In this paper, we propose a variant of sticker systems which uses molecules with complex structures. Since the original sticker systems (Paun et al. (1998) [2, 8]) working on double strands of DNA have been studied as a formal model for self-assembly in DNA computing, we extend the sticker systems to working on more complex (higher-order) structures of DNA molecules. The advantage of sticker systems with complex structures is that augmented with weak codings we can obtain the characterization of recursively enumerable languages by using only sticking (hybridization) operations for complex molecules, while the usual sticker systems require more complicated operations such as the simultaneous use of couples of dominoes or coherent computations besides morphisms.     

一种UML2的交互的形式化语义

UML2(unified modeling language2.x)的规范为其交互定义了一种基于事件发生轨迹的语义,弥补了之前版本在语义上的欠缺。但是此语义是用自然语言(英语)描述的,不够精确、不一致,并且很多细节解释得不够清楚和完备。利用集合论以组合定义的方式形式化语义,并且证明了形式化后交互的语义为拟序集,此拟序集的线性化恰好就是规范所定义的轨迹集。此形式化语义可以作为UML2交互规范的很好的补充,不但有助于UML2交互的理解,还为UML2交互的应用和研究奠定了坚实的理论基础。     

A two-level costate prediction algorithm for non-linear systems

A two level costate prediction algorithm is developed for the optimisation of non-linear discrete dynamical systems.The algorithm is proved to converge under fairly mild conditions. The algorithm appears to require substantially smaller computation time and storage than previous two level algorithms. The method is illustrated on a practical problem of optimisation of turbogenerator transient performance.     

A conceptual design aid environment for expert-database systems

With the actual penetration of expert systems into the business world, the question is, how the expert system idea can be used to enhance the existing information systems with more intelligence in usage and operation. This interest is not surprising due to the advancement of the fifth generation of computer technology, and avid interest in the field of Artificial Intelligence. Therefore design of an information system for an application becomes more complex, and the inability of the human designer to deal with it increases. For designing intelligent systems, we have to be able to forecast the behavior of the information system more precisely before implementing it, i.e. we'have to support the specification process.Clearly the technology, such as Data base systems, is leading on efficiency issues as those needed for the construction, retrieval and manipulation of large shared data base. On the other hand, the AI techniques have improved significantly with function such as deductive reasoning and natural language processing. It is important to find way to merge these technologies into one mainstream of computing. A meeting point for the two areas is the issue of conceptual knowledge modelling, so that models can be created that will define the role and the ways to use data in AI systems. In the framework of this study, one possible expert system design aid environment has been suggested to assist the designer in his work.In a conceptual modelling environment a model is given for analysing complex real world problems known as the Conceptual Knowledge Model (CKM), represented by a Graphical and a Formal Representation. The Graphical Representation consists of three graphs: Conceptual Requirement Graph, Conceptual Behavior Graph, and Conceptual Structure Graph. These graphs are developed by involving the expert during the design process. The graphs are then transformed into first-order predicate logic to represent the logical axioms of a theory, which constitutes the knowledge base of the Expert System. The model suggested here is a step towards closing the gap between the theory of the conventional data base theory and AI databases.     

An architectural application framework for evolving distributed systems

In this paper, we present an object-oriented application framework to support the development of evolving distributed systems. The framework combines concepts of the object-oriented paradigm with those of architectural design. The result is a framework which supports extensible and reusable configurations of distributed components. The framework addresses the problem of evolution by allowing the addition, replacement and extension of components of a configuration. Evolution is also possible at run time, where a configuration can change dynamically depending on a particular event. The paper outlines the fundamental aspects of our framework and presents a case study, which illustrates its application.