Graphics Programs Reference
In-Depth Information
1
INTRODUCTION
The recent rapid
ad
vances in different technological fields have led to remark-
able increases in system complexity in several application areas. A represen-
tative example of this process is provided by the area of computer engineer-
ing, where the advances in the fields of VLSI and software design have led to
complex distributed computing systems whose capabilities largely surpass
those of traditional computers.
The effective exploitation of the possibilities offered by technological inno-
vations requires adequate tools to describe, to model, and to analyse the
various design alternatives. In particular, since system performance is of-
ten the ultimate goal behind increased system complexity, tools that allow
the relative merits and the intrinsic quality of the possible solutions to be
quantified are badly needed.
Many different paradigms for the description of complex systems heve re-
cently been developed, but only a few of these allow the integration of per-
formance analysis concepts within the description itself. Petri nets are one
of the few paradigms allowing this integration.
Petri Nets (PNs) are a graphical tool for the formal description of systems
whose dynamics are characterized by concurrency, synchronization, mutual
exclusion, and conflict, which are typical features of distributed environ-
ments. PNs incorporate a notion of (distributed) state and a rule for state
change that allow them to capture both the static and the dynamic charac-
teristics of a real system.
PNs can be fruitfully applied in quite a diverse variety of fields, ranging from
distributed computing — in its architectural, algorithmic, hardware, and
software components — to flexible manufacturing, communication protocols,
control systems, transportation, banking, and organization of work.
In this topic we are mainly interested in the application of PNs for per-
formance evaluation of distributed systems, with examples taken from the
computing, communications, and manufacturing fields, using either simula-
tion or numerical methods. However, it is important to mention that PNs
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