PHYSICAL CONTEXT - FREE REUSABILITY OF MODELLING
COMPONENTS WITH OBJECT ORIENTED LANGUAGES
M´onica Guti´errez, J. J. Ramos, M.A. Piera
Monica.Gutierrez@uab.es
Dpt. de Telecomunicaciones e Ingenier´ia de Sistemas
Universitat Aut`onoma de Barcelona.
ABSTRACT
A main eŽort of the research community has been focused in creating modelling methodologies
and tools able to simplify the modelling process. The tools currently available
use the mathematical formalism as the means to formulate the behaviour of a system.
The main approach to the reduction of the modelling burden is to provide with reuse
of predefined modelling components in order to support a structured modelling process.
However, the reusability of modelling components becomes diącult in contexts
to which they were not defined for. This paper introduces the Physical modelling Language
(PML) an object-oriented language. It defines a new formalism to represent the
system behaviour. Its objective is ensure the context independent reusability of the modelling
components. Throughout the paper, the main distinctive features of PML will be
illustrated by means of a modelling example.
Keywords: Object-oriented modelling, simulation, model reusability, modelling
automation.
1 INTRODUCTION
The modelling and simulation techniques have been
and continue being fundamental tools in areas like engineering
and physical and biological sciences. However,
there still remain application domains where
they are scarcely used in spite of the potential bene-
fits of using these techniques. To cope with the growing
demands for simulation models of ever increasing
complex industrial systems, the research community
eŽort has been mainly focused in creating new
modelling methodologies and tools which simplify the
modelling process. Structured modelling and reuse
of predefined modelling components is an approach
widely accepted by most of the tools currently available.
Object-oriented modelling is a well known paradigm
to support in a natural way structured modelling
and reuse of predefined modelling components
(Andersson, 1994; Nilsson, 1993; Cellier,
1991). The object orientation configures a modelling
methodology where the behaviour of a physical component
can be encapsulated in a modelling component
which can be aggregated to other components in order
to build new structured components. Most of the
object-oriented modelling tools are based in the mathematical
formalism as the means to formulate the behaviour
of a physical component within the modelling
component (Modelica-Association, 2000; Cobas and
Al., 1999). The behaviour mathematical formulation
is defined once the modeler states which of the phenomena
occurring in the system should be represented
by the model, as well as the detail used to formulate
these phenomena. However, diŽerent experimentation
frameworks may introduce diŽerent requirements
in relation to the phenomena which must be represented
and their formulation detail. Therefore, the
reusability of a modelling component can not be assured
when it has been defined to represent a system
component in a particular context, i.e., when the
modelling component formulate the system dynamics
which is of interest for the experimentation purposes.
This paper discusses the need of a behaviour representation
formalism able to assure the reusability of
a predefined modelling component regardless of the
reusing physical context. The Physical Modelling
Language language (PML) will be used for this purpose.
PML is an object oriented language designed
to overcome the limitations with respect to reusability
introduced by the mathematical formalism. Sec-
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