Summary: Networks of Identical Multi­Clock Timed
Processes 1
Parosh Aziz Abdulla a,2 Johann Deneux a,3 Pritha Mahata b,4
a Uppsala University, Sweden
b University of Newcastle, Australia
Abstract
We consider verification of safety properties for parameterized systems of timed pro­
cesses, so called timed networks. A timed network consists of a finite state process,
called a controller, and an arbitrary set of identical timed processes. In a previ­
ous work, we showed that checking safety properties is decidable in the case where
each timed process is equipped with a single real­valued clock. It was left open
whether the result could be extended to multi­clock timed networks. We show that
the problem becomes undecidable when each timed process has two clocks. On the
other hand, we show that the problem is decidable when clocks range over a discrete
time domain. This decidability result holds when processes have any finite number
of clocks.
We also study two syntactical subclasses of (dense) timed networks: open and
closed timed networks. In open timed networks, all clock constraints are strict (thus
corresponds to syntactic removal of equality testing), while in closed timed net­
works, all clock constraints are non­strict. We show that the problem remains un­

Source: Abdulla, Parosh Aziz - Department of Information Technology, Uppsala Universitet

Collections: Computer Technologies and Information Sciences