P.H.A. van der Putten

Object-oriented modelling and specification using SHE

Industry is facing a crisis in the design of complex hardware/software systems. Due to the increasing complexity, the gap between the generation of a product idea and the realisation of a working system is expanding rapidly. To manage complexity and to shorten design cycles, industry is forced to look at system-level languages towards specification and design. The (formal) system-level modelling language called POOSL is very expressive and is able to model dynamic hard real-time behaviour and to (visually) capture static (architecture and topology) structure in an object-oriented fashion. The language integrates a process part, based on the process algebra CCS, with a data part, based on the concepts of traditional object-oriented programming languages and it is equipped with a formal semantics. Currently, a number of automated software tools (model editing, simulator and compiler tools) are available in an environment called SHESim. These tools allow visual entry of structure and topology of the system, whereas dynamic behaviour of individual processes is expressed in an expressive imperative language. The formal semantics of POOSL provides a solid basis for the application of verification and performance analysis techniques and establishing a rigorous connection to existing analysis tools.

System level design methodology

There are many fundamental problems in the design of object-oriented methods that support the development of formal executable models on a system level, and that are suitable for hardware/software co-specification. System level description formalisms should combine concepts expressive enough to model the essentials of a system on the right level of abstraction. This paper reports experiences in developing a specification and design method SHE (Software/Hardware Engineering) which is based on a formal language POOSL (Parallel Object-Oriented Specification Language). The method offers a path from an informal specification to a unified formal model that enables evaluation of system properties. This paper describes concrete new results as well as an approach towards research on system level methodology.

System level modelling for hardware/software systems

Industry is facing a crisis in the design of complex hardware/software systems. Due to the increasing complexity, the gap between the generation of a product idea and the realisation of a working system is expanding rapidly. To manage complexity and to shorten design cycles, industry is forced to look at system level languages towards specification and design. We report on the system level modelling language called POOSL. The language is very expressive and is able to model dynamic hard real time behaviour as well as static (architecture and topology) structure in an object oriented fashion. The language integrates a process part, based on the process algebra CCS, with a data part, based on the concepts of traditional object oriented programming languages. Unlike many modelling languages today, POOSL is equipped with a complete mathematical semantics. Currently a number of automated software tools (model editing simulator and compiler tools) are available. It is shown how the language and tools allow the estimation of a performance parameter of a datalink protocol.

Systematic development of industrial control systems using software/hardware engineering

SHE (software/hardware engineering) is a new object-oriented analysis, specification and design method for complex reactive hardware/software systems. SHE is based on the formal specification language POOSL and a design framework for guiding analysis and design activities. This paper reports on the applicability of the SHE method for the specification and design of the control subsystem of a new generation of industrial mailing machines.

Behaviour-preserving transformations in SHE: a formal approach to architecture design

SHE (Software/Hardware Engineering) is an object-oriented analysis, specification and design method for complex reactive hardware/software systems. SHE is based on the formal specification language POOSL and a design framework guiding the analysis and design activities. During analysis several graphical models are produced. These models are formalized in a textual representation in the POOSL language. The obtained POOSL description describes both behaviour and initial system structure. During design the initial system structure may have to be adjusted or refined due to architectural constraints and design decisions. For this purpose so-called behaviour-preserving transformations are used. These transformations allow structure modifications in a graphical way and they allow the automatic change of the POOSL specification during interactive system simulation. This paper reports the development of a formal basis for design transformations and shows their applicability.

System level models for real-time communication

This paper reports on system level modelling techniques for specification and verification of real-time distributed systems. The approach uses an object-oriented description technique that yields formal executable system level models, suitable for hardware/software co-specification. The focus in this paper is on finding system level abstractions for modelling real-time communication in distributed systems. A generic LAN model is presented that models the properties of tightness, bounded transmission delay, and bounded omission degree. The model is evaluated for the quality of verification of real-time properties. This leads to the definition of research goals in new fields of formal verification, such as time continuous qualitative property verification, and probabilistic quantitative verification.

On the fundamental design gap in terabit per second packet switching

We discuss the gap we experience in an industrial design path of high-speed packet switches. As bandwidth demand exceeds progress in CMOS technology, system architects are forced to abandon familiar design solutions and make fundamental changes to their architectures at an increasingly faster pace. We investigate design methods to decrease the risk of such changes and to provide a structured and confident transition from conceptual system-level models to hardware descriptions. It appears that the design gap is caused by differences between language primitives and underlying concepts of system-level design languages and hardware description languages. We substantiate the need for expressive system-level modeling concepts and show that the gap is actually caused by a fundamental interpretation mismatch between models and descriptions. Based on a comparison of existing system-level synthesis methods with the interpretation gap, we propose to decrease the gap by using modeling patterns.