92,672 research outputs found
MTL-Model Checking of One-Clock Parametric Timed Automata is Undecidable
Parametric timed automata extend timed automata (Alur and Dill, 1991) in that
they allow the specification of parametric bounds on the clock values. Since
their introduction in 1993 by Alur, Henzinger, and Vardi, it is known that the
emptiness problem for parametric timed automata with one clock is decidable,
whereas it is undecidable if the automaton uses three or more parametric
clocks. The problem is open for parametric timed automata with two parametric
clocks. Metric temporal logic, MTL for short, is a widely used specification
language for real-time systems. MTL-model checking of timed automata is
decidable, no matter how many clocks are used in the timed automaton. In this
paper, we prove that MTL-model checking for parametric timed automata is
undecidable, even if the automaton uses only one clock and one parameter and is
deterministic.Comment: In Proceedings SynCoP 2014, arXiv:1403.784
Revisiting Reachability in Timed Automata
We revisit a fundamental result in real-time verification, namely that the
binary reachability relation between configurations of a given timed automaton
is definable in linear arithmetic over the integers and reals. In this paper we
give a new and simpler proof of this result, building on the well-known
reachability analysis of timed automata involving difference bound matrices.
Using this new proof, we give an exponential-space procedure for model checking
the reachability fragment of the logic parametric TCTL. Finally we show that
the latter problem is NEXPTIME-hard
Behavioral models of digital IC ports from measured transient waveforms
This paper addresses the behavioral modeling of output ports of digital integrated circuits via the identification of nonlinear parametric models. The aim of the approach is to produce models for signal integrity (SI) simulation directly from the measured transient responses of the devices. The modeling process is thoroughly described and an experimental demonstration of its feasibility is give
Single-Piece State-Space Behavioral Models for IC Output Buffers
In this paper enhancements of parametric behavioral models for the output buffers of digital ICs are explored. A model based on a single-piece structure, which offers improved accuracy in describing state transition events for arbitrary load conditions, is proposed. This model exploits the potentiality of local-linear state-space parametric relations. These relations can be effectively estimated from input-output port responses only, and provide better stability properties and improved efficienc
M[pi]log, Macromodeling via parametric identification of logic gates
This paper addresses the development of computational models of digital integrated circuit input and output buffers via the identification of nonlinear parametric models. The obtained models run in standard circuit simulation environments, offer improved accuracy and good numerical efficiency, and do not disclose information on the structure of the modeled devices. The paper reviews the basics of the parametric identification approach and illustrates its most recent extensions to handle temperature and supply voltage variations as well as power supply ports and tristate devices
On the verification of parametric and real-time systems
2009 - 2010Parametric and Real-Time Systems play a central role in the theory underlying
the Verification and Synthesis problems.
Real-time systems are present everywhere and are used in safety critical
applications, such as flight controllers. Failures in such systems can be
very expensive and even life threatening and, moreover, they are quite
hard to design and verify. For these reasons, the development of formal
methods for the modeling and analysis of safety-critical systems is
an active area of computer science research.
The standard formalism used to specify the wished behaviour of a realtime
system is temporal logic. Traditional temporal logics, such as linear
temporal logic (LTL), allow only qualitative assertions about the temporal
ordering of events. However, in several circumstances, for assessing the
efficiency of the system being modeled, it may be useful to have additional
quantitative guarantees. An extension of LTL with a real-time semantics
is given by the Metric Interval Temporal Logic (MITL), where changes
of truth values happen according to a splitting of the line of non-negative
reals into intervals.
However, even with quantitative temporal logics, we would actually like
to find out what quantitative bounds can be placed on the logic operators.
In this thesis we face with the above problem proposing a parametric
extension of MITL, that is the parametric metric interval temporal logic
(PMITL), which allows to introduce parameters within intervals . For this
logic, we study decision problems which are the analogous of satisfiability,
validity and model-checking problems for non-parametric temporal
logic. PMITL turns out to be decidable and we show that, when parameter
valuations give only non-singular sets, the considered problems are all
decidable, EXPSPACE-complete, and have the same complexity as in MITL.
Moreover, we investigate the computational complexity of these problems
for natural fragments of PMITL, and show that in meaningful fragments
of the logic they are PSPACE-complete.
We also consider a remarkable problem expressed by queries where the
values that each parameter may assume are either existentially or universally
quantified. We solve this problem in several cases and we propose an
algorithm in EXPSPACE.
Another interesting application of the temporal logic is when it is used
to express specification of concurrent programs, where programs and properties
are formalized as regular languages of infinite words. In this case,
the verification problem (whether the program satisfies the specification)
corresponds to solve the language inclusion problem.
In the second part of this thesis we consider the Synthesis problem for realtime
systems, investigating the applicability of automata constructions that
avoid determinization for solving the language inclusion problem and the
realizability problem for real-time logics. Since Safra’s determinization
procedure is difficult to implement, we present Safraless algorithms for
automata on infinite timed words. [edited by author]IX n.s
Parametric Macromodels of Drivers for SSN Simulations
This paper addresses the modeling of output and power supply ports of digital drivers for accurate and efficient SSN simulations. The proposed macromodels are defined by parametric relations, whose parameters are estimated from measured or simulated port transient responses, and are implemented as SPICE subcircuits. The modeling technique is applied to commercial high-speed devices and a realistic simulation example is shown
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