Ankündigung eines Vortrags im Graduiertenkolleg

### Gastvortrag

## "From Discrete Event Systems to Continuous models:

A Petri Nets based coherent view"

### 3. Dezember 2001

### Prof. Manuel Silva

Departamento de Informatica e Ingeniería de Sistemas

Centro Politécnico Superior, Universidad de Zaragoza

**Termin**

Montag, 3. Dezember 2001, 10 Uhr

**Ort**

TU Berlin, Einsteinufer 17, Gebäude EN, Raum 719

**Inhalt**

Fluidification of Petri net models leads to continuous and hybrid systems.
Surprisingly, not all DEDS models can be fluidified. In fact,
fluidification requires "big populations" and DEDS are not always
behaviourally monotonic with respect to population homothetic growth.
First-order fluidification of stochastic (discrete) PN models leads to
deterministic and continuous models. Nevertheless, basic qualitative
properties, like absence of deadlocks are not preseved in general (e.g. you
may have a live and bounded discrete time-stochastic model, while the
corresponding continuous model is unbounded and non-live!). Therefore
results concerning continuisable net subclasses are required.

Another interesting reflection concerning continuous net models is that,
even if the continuous approximation (or view) is stable, it may happen
that no steady-state exists (a clearly non-linear behaviour for the continuous
relaxed model). This is another "unexpected" property, in the sense that
works in the field of continuous models usually assume its existence.

The presentation will also introduce some design problems, like the
computation of a minimal initial marking, that surprisingly happens to
be polynomial for certain net subclasses. Some control results will be
introduced, making a bridge to scheduling in the underlying discrete model.