MoDeST: A compositional modeling formalism for hard and softly timed systems (original) (raw)

MoDeST - A Modelling and Description Language for Stochastic Timed Systems

Process Algebra and Probabilistic Methods, 2001

This paper presents a modelling language, called MoDeST, for describing the behaviour of discrete event systems. The language combines conventional programming constructs - such as iteration, al- ternatives, atomic statements, and exception handling - with means to describe complexsystems in a compositional manner. In addition, MoDeST incorporates means to describe important phenomena such as non-determinism, probabilistic branching, and hard real-time

Specification of Stochastic Properties in Real-Time Systems

1996

In this paper we present a new approach to the formal speci cation of distributed real-time systems using the formal description technique LOTOS together with a stochastic temporal logic STL. This approach previously presented in the context of LOTOS/QTL, is characterized by a separation of concerns. The functional behaviour is described in LOTOS without regard for the time critical constraints. The speci cation is then extended with precise real-time requirements written in STL. We present a method to generate a timing event scheduler from the requirements in order to monitor the functional behaviour.

A Formal Approach to Modelling Time Properties of Service-Oriented Systems?

2000

We provide a formal model for expressing and analysing time-related properties of service-oriented systems. Our approach extends SRML, a high-level modelling language that we have been developing in the SENSORIA project. We introduce new primitives for SRML that capture several kinds of delays that can occur during service provision (e.g., the time taken by components to process events and perform computations, the time taken by the SOA middleware for discovering, selecting and binding services, etc.). Finally, we show how we can use the stochastic process algebra PEPA and its development environment to represent and analyse time properties of SRML models.

Formal Techniques, Modelling and Analysis of Timed and Fault-Tolerant Systems

Lecture Notes in Computer Science, 2004

We consider a general notion of timed automata with inputdetermined guards and show that they admit a robust logical framework along the lines of [6], in terms of a monadic second order logic characterisation and an expressively complete timed temporal logic. We then generalise these automata using the notion of recursive operators introduced by Henzinger, Raskin, and Schobbens [9], and show that they admit a similar logical framework. These results hold in the "pointwise" semantics. We finally use this framework to show that the real-time logic MITL of Alur et al [2] is expressively complete with respect to an MSO corresponding to an appropriate input-determined operator.

Safety Contracts for Timed Reactive Components in SysML

Lecture Notes in Computer Science, 2014

A variety of system design and architecture description languages, such as SysML, UML or AADL, allows the decomposition of complex system designs into communicating timed components. In this paper we consider the contract-based specification of such components. A contract is a pair formed of an assumption, which is an abstraction of the component's environment, and a guarantee, which is an abstraction of the component's behavior given that the environment behaves according to the assumption. Thus, a contract concentrates on a specific aspect of the component's functionality and on a subset of its interface, which makes it relatively simpler to specify. Contracts may be used as an aid for hierarchical decomposition during design or for verification of properties of composites. This paper defines contracts for components formalized as a variant of timed input/output automata, introduces compositional results allowing to reason with contracts and shows how contracts can be used in a high-level modeling language (SysML) for specification and verification, based on an example extracted from a real-life system.

An industrial-strength formal method

Abstract. This paper gives an impression of the language modest, a modelling and description language for stochastic and timed systems, and reports on applications of this language to a variety of industrial case studies. The language and its accompanying tool environment, motor, support the modular description and analysis of reactive systems while covering both functional and non-functional system aspects such as hard and soft real-time, and quality-of-service aspects.

Specification and analysis of soft real-time systems: Quantity and quality

1999

Abstract This paper presents a process algebra for specifying soft real-time constraints in a compositional way. For these soft constraints we take a stochastic point of view and allow arbitrary probability distributions to express delays of activities. The semantics of this process algebra is given in terms of stochastic automata, a variant of timed automata where clocks are initialised randomly and run backwards.

Formal Specification, Verification and Simulation of Time-Dependent Systems: a Timed Process Algebra Approach

Electronic Notes in Theoretical Computer Science, 1998

In this paper, we present an approach to speci cation, veri cation and validation of concurrent time-dependent systems which is centered on a timed process algebra language, called RTL (for real time LOTOS). Our approach is supported by a tool named RTL-Analyzer, that allows automatic veri cation and validation of RTL speci cations. RTL is a temporal extension of basic LOTOS language which expresses and handles temporal constraints associated with actions. First, we present and justify the use of RTL to specify concurrent time-dependent systems. Then, the main characteristics and functionalities of the RTL-Analyzer are presented with details for systems veri cation and validation using our approach. An example of a time-dependent system is given and it is speci ed and analyzed by our tool. Finally, we compare our approach with others proposed in the literature.

Specifying Timing Properties of Reactive Systems with TLC

1997

Reactive systems usually contain several parallel processes, which are running concurrently. Therefore, it is essential to study and analyse each process based on its local time. Because of the introduction of local clocks, the temporal logic TLC is particularly suitable for the speci cation of those systems such as reactive systems, where granularity of time is needed. In this paper, we discuss the formal speci cation of reactive systems based on TLC. We in particular present a method to describe timing properties of reactive systems using TLC. In this logic, a system and its corresponding properties are represented as formulas, and the properties can be therefore directly reasoned about from the speci cation of the system.