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Discrete event simulation of
Mediterranean fruit flies propagation
Jean Baptiste Filippi – Paul Bisgambiglia – Julie Acquaviva – Jean-François Santucci.
UMR CNRS 6134, Université de Corse
{filippi, bisgambi, jacquaviva, santucci}@univ-corse.fr
INTRODUCTION
Most simulation models in environmental science
are built by ecologist. The evident advantages of
this fact is that all processes are well identified and
understood, but the bottom line is that the computer
implementation of the model is often poorly
designed and hardly reusable. This result is partly
due to the fact that only a few environmental
modeling and simulation tools exists and even
fewer that are based on strong modeling and
simulation theory concepts.
The other cause of the lack of efficiency in some
environmental simulation models is that domain
specialists lacks metaphors to conceptualize the
world in computerized forms
Those metaphors are found in the form of modeling
paradigms, such as multi-agent or cellular
automata. Many of those paradigms are in use
today and implemented in specific modeling and
simulation software.
Specialists often uses one of those paradigms but,
what is becoming difficult is not only to formulate
but also to conceive higher level problems, whose
complexity is such that they escape definition
through a single metaphor.
To build effectively such models, one must couple
different sub-models that might have been built
using different paradigms. Those kind of models
are called multi-models, and have been introduced
by [Orën, 1991] later extended by [Fishwick, 1995].
To achieve reusability in Multi-modeling it is
necessary to use of a formal framework that is
sufficiently open and flexible to enable the
integration of several distinct modeling techniques.
We propose to base our formal framework on a
methodology called DEVS introduced by [Zeigler,
2000].
DEVS is a set-theoretic formalism that includes a
formal representation capable of mathematical
manipulation just as differential equations serves
this role for continuous systems. It is possible to
perform formal verifications of a model using
DEVS formal representation thus decreasing testing
and implementation time. DEVS formalism also
presents an explicit separation between the phases
of modeling and simulation, DEVS models are
directly simulable in a specific experimental frame.
The Experimental Frame (EF) describes a limited
set of circumstances under which a system (real or
model) is to be observed or subjected to
experimentation. As such, it reflects the objectives
of the experimenter who performs experiments on a
real system or, through simulation, on a model.
DEVS needs to be adapted and extended when
replaced in a domain-specific context. A wide set of
techniques that derives from DEVS, such as Cell-
DEVS [Wainer and Giambiasi, 2001] or JAMES
[Schattenberg and Uhrmacher, 2001] have already
been developed to serve some domain specific
needs [Zeigler, 2000]..
From a software engineering perspective, we
propose to base our approach on Object Oriented
design concepts [Hill, 1996]. Those concepts had
led to various analysis methods, among those
methods, UML (Unified modeling language)
[Gamma et al.] which now became a standard.
UML and the modeling and simulation field should
be distinguished despite the name and strong
similarities. We are also making the use of "design
patterns" [Gamma et al.,] to reduce the overall
complexity of the global classes architecture of the
software framework.
THE JAVA DEVS TOOLKIT
JDEVS toolkit is composed of five independent
modules. They can interact with other modules that
are already developed and some elements,
including the java simulation kernel, might be
changed for better performance.
Modeling and simulation kernel
The modeling and simulation kernel is a java
implementation of the DEVS formalism. Atomics
and coupled models are described as follow.
Atomic DEVS models definition
The DEVS formalism is offering well defined
interfaces for the description of systems. The
concept of model abstraction permits to use models
that are coded in various object oriented languages.
Those models are then accessed thought a software
interface specified in DEVS.
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