Regular Canonical Systems

Durational transition systems are finite transition systems where every transition is additionally equipped with a duration. We consider the problem of interpreting /spl mu/-formulas over durational transition systems. In case the formula contains only operations minimum, maximum, addition, and sequencing, we show that the interpretation ist not only computable but (up to a linear factor) as efficiently computable as the interpretation of /spl mu/-formulas over ordinary finite transition systems.

We study the following problems for strong and weak bisimulation equivalence: given a labelled Petri net and a finite transition system, are they equivalent?; given a labelled Petri net, is it equivalent to some (unspecified) finite transition system? We show that both problems are decidable for strong bisimulation and undecidable for weak bisimulation.

Linear reachability problems and minimal solutions to linear Diophantine equation systems

The linear reachability problem is to decide whether there is an execution path in a given finite state transition system such that the counts of labels on the path satisfy a given linear constraint. Using results on minimal solutions (in nonnegative integers) for linear Diophantine systems, we obtain new complexity results for the problem, as well as for other linear counting problems of finite state transition systems and timed automata. In contrast to previously known results, the complexity bounds obtained in this paper are polynomial in the size of the transition system in consideration, when the linear constraint is fixed.

In this paper, we study the problem of revising Linear Temporal Logic (LTL) formulas that capture specifications for optimal planning over weighted transition systems. Namely, it is assumed that the model of the system is a weighted finite state transition system. The LTL specification captures the system requirements which must be satisfied by a plan which costs less than a certain cost budget. If the cost bounds cannot be satisfied with the initial specification, then it is desirable to return to the user a specification that can be satisfied on the system within the desired cost budget. We prove that the specification revision problem for automata-based optimal planning is NP-complete. In order to provide exact solutions to the problem, we present an Integer Linear Program (ILP) and a Mixed-Integer Linear Program (MILP) formulation for different versions of the problem. Finally, we indicate that a Linear Program (LP) relaxation can compute fast approximations to the problem.

The Nested Context Language is a multimedia authoring language which is part of the standard for digital television in Brazil and in Latin America and the ITU standard for IPTV services. The need for proper support for the development of NCL applications is growing with the increasing demand for digital TV applications. Rigorous means to assure that multimedia presentations in NCL will behave as expected is an example. Since NCL applications may be understood as finite transition systems, standard model-based verification techniques directly apply. This paper discusses a formalization of NCL semantics and its realization in a verification tool.

We study an automata-theoretic approach to planning for temporally extended goals. Specifically, we devise techniques based on nonemptiness of Buchi automata on infinite words, to synthesize sequential and conditional plans in a generalized setting in which we have that: goals are general temporal properties of desired execution; dynamic systems are represented by finite transition systems; incomplete information on the initial situation is allowed; and states are only partially observable. We prove that the techniques proposed are optimal wrt the worst case complexity of the problem. Thanks to the scalability of the nonemptiness algorithms, the techniques presented here promise to be applicable to fairly large systems, notwithstanding the intrinsic complexity of the problem.

The procedures for utilizing substructuring and static condensation in structural analysis are well known. However, until recently there have been no general‐purpose structural mechanics computer systems that offer multi‐level substructuring combined with a convenient method for defining the structural model. Now that such systems are available, engineers must decide when substructuring techniques are useful. Substructuring, with and without condensation, has proved to be highly efficient in the analysis of certain classes of structure. It can reduce computer costs by a factor of from 2 to 100. Yet, indiscriminate use of condensation may result in unnecessary and expensive computations. This paper examines the advantages and disadvantages of substructuring relative to data entry and computational efficiency. Guidelines are proposed for engineers to follow when using substructuring in the analysis of linear and nonlinear structures. The FINITE system is used to illustrate actual implementation of substructuring features in a general purpose finite element system.

In this paper, we consider the problem of synthesizing correct-by-construction controllers for discrete-time dynamical systems. A commonly adopted approach in the literature is to abstract the dynamical system into a Finite Transition System (FTS) and thus convert the problem into a two player game between the environment and the system on the FTS. The controller design problem can then be solved using synthesis tools for general linear temporal logic or generalized reactivity(1) specifications. In this article, we propose a new abstraction algorithm. Instead of generating a single FTS to represent the system, we generate two FTSs, which are under- and over-approximations of the original dynamical system. We further develop an iterative abstraction scheme by exploiting the concept of winning sets, i.e., the sets of states for which there exists a winning strategy for the system. Finally, the efficiency of the new abstraction algorithm is illustrated by numerical examples.

Regions of Petri nets with a/sync connections

We present a semantic method to check the finiteness of CCS terms. The method is interpretative, i.e. it is based on a non-standard CCS operational semantics. According to this semantics it is always possible, given a processp, to build a finite state transition system which, if a condition holds, is a finite representation ofp; otherwise it is a suitable approximation of its semantic behaviour. The method is able to decide the finiteness of a CCS term in a larger number of cases than those captured by known syntactic criteria.

This paper addresses the issue of automatic service composition. We first develop a framework in which the exported behavior of a service is described in terms of a so-called execution tree, that is an abstraction for its possible executions. We then study the case in which such exported behavior (i.e. the execution tree of the service) can be represented by a finite state machine (i.e. finite state transition system). In this specific setting, we devise sound, complete and terminating techniques both to check for the existence of a composition, and to return a composition, if one exists. We also analyze the computational complexity of the proposed algorithms. Finally, we present an open source prototype tool, called [Formula: see text] (E-Service Composer), that implements our composition technique. To the best of our knowledge, our work is the first attempt to provide a provably correct technique for the automatic synthesis of service composition, in a framework where the behavior of services is explicitly specified.

T-systems are generalisations of marked graph Petri nets. This paper describes synthesis algorithms that allow bounded or unbounded T-systems to be derived from finite or infinite labelled transition systems satisfying a set of necessary properties. These properties can thus be interpreted as axioms characterising T-system state spaces.

This paper describes the implementation of predicate abstraction techniques to automatically compute symbolic backward reachable sets of high dimensional piecewise affine hybrid automata, used to model Delta-Notch biological cell signaling networks. These automata are analyzed by creating an abstraction of the hybrid model, which is a finite state discrete transition system, and then performing the computation on the abstracted system. All the steps, from model generation to the simplification of the reachable set, have been automated using a variety of decision procedure and theorem-proving tools. The concluding example computes the reach set for a four cell network with 8 continuous and 256 discrete states. This demonstrates the feasibility of using these tools to compute on high dimensional hybrid automata, to provide deeper insight into realistic biological systems.

A bumpless hybrid supervisory control algorithm for the formation of unmanned helicopters