62 research outputs found
Conflict vs causality in event structures
Event structures are one of the best known models for concurrency. Many variants of the basic model and many possible notions of equivalence for them have been devised in the literature. In this paper, we study how the spectrum of equivalences for Labelled Prime Event Structures built by Van Glabbeek and Goltz changes if we consider two simplified notions of event structures: the first is obtained by removing the causality relation (Coherence Spaces) and the second by removing the conflict relation (Elementary Event Structures). As expected, in both cases the spectrum turns out to be simplified, since some notions of equivalence coincide in the simplified settings; actually, we prove that removing causality simplifies the spectrum considerably more than removing conflict. Furthermore, while the labeling of events and their cardinality play no role when removing causality, both the labeling function and the cardinality of the event set dramatically influence the spectrum of equivalences in the conflict-free setting
A CuCh Interpretation of an Object-Oriented Language1 1Partially supported by MURST Cofin '99 TOSCA.
AbstractBöhm's CuCh machine extends the pure lambda-calculus with algebraic data types and provides the possibility of defining functions over disjoint sums of algebras. We exploit such natural form of overloading to define a functional interpretation of a simple, but significant fragment of a typical objectoriented classbased language
On Model Based Synthesis of Embedded Control Software
Many Embedded Systems are indeed Software Based Control Systems (SBCSs), that
is control systems whose controller consists of control software running on a
microcontroller device. This motivates investigation on Formal Model Based
Design approaches for control software. Given the formal model of a plant as a
Discrete Time Linear Hybrid System and the implementation specifications (that
is, number of bits in the Analog-to-Digital (AD) conversion)
correct-by-construction control software can be automatically generated from
System Level Formal Specifications of the closed loop system (that is, safety
and liveness requirements), by computing a suitable finite abstraction of the
plant.
With respect to given implementation specifications, the automatically
generated code implements a time optimal control strategy (in terms of set-up
time), has a Worst Case Execution Time linear in the number of AD bits , but
unfortunately, its size grows exponentially with respect to . In many
embedded systems, there are severe restrictions on the computational resources
(such as memory or computational power) available to microcontroller devices.
This paper addresses model based synthesis of control software by trading
system level non-functional requirements (such us optimal set-up time, ripple)
with software non-functional requirements (its footprint). Our experimental
results show the effectiveness of our approach: for the inverted pendulum
benchmark, by using a quantization schema with 12 bits, the size of the small
controller is less than 6% of the size of the time optimal one.Comment: Accepted for publication by EMSOFT 2012. arXiv admin note:
substantial text overlap with arXiv:1107.5638,arXiv:1207.409
On minimising the maximum expected verification time
Cyber Physical Systems (CPSs) consist of hardware and software components. To verify that the whole (i.e., software + hardware) system meets the given specifications, exhaustive simulation-based approaches (Hardware In the Loop Simulation, HILS) can be effectively used by first generating all relevant simulation scenarios (i.e., sequences of disturbances) and then actually simulating all of them (verification phase). When considering the whole verification activity, we see that the above mentioned verification phase is repeated until no error is found. Accordingly, in order to minimise the time taken by the whole verification activity, in each verification phase we should, ideally, start by simulating scenarios witnessing errors (counterexamples). Of course, to know beforehand the set of such scenarios is not feasible. In this paper we show how to select scenarios so as to minimise the Worst Case Expected Verification Tim
Model Based Synthesis of Control Software from System Level Formal Specifications
Many Embedded Systems are indeed Software Based Control Systems, that is
control systems whose controller consists of control software running on a
microcontroller device. This motivates investigation on Formal Model Based
Design approaches for automatic synthesis of embedded systems control software.
We present an algorithm, along with a tool QKS implementing it, that from a
formal model (as a Discrete Time Linear Hybrid System) of the controlled system
(plant), implementation specifications (that is, number of bits in the
Analog-to-Digital, AD, conversion) and System Level Formal Specifications (that
is, safety and liveness requirements for the closed loop system) returns
correct-by-construction control software that has a Worst Case Execution Time
(WCET) linear in the number of AD bits and meets the given specifications.
We show feasibility of our approach by presenting experimental results on
using it to synthesize control software for a buck DC-DC converter, a widely
used mixed-mode analog circuit, and for the inverted pendulum.Comment: Accepted for publication by ACM Transactions on Software Engineering
and Methodology (TOSEM
Quantized Feedback Control Software Synthesis from System Level Formal Specifications for Buck DC/DC Converters
Many Embedded Systems are indeed Software Based Control Systems (SBCSs), that
is control systems whose controller consists of control software running on a
microcontroller device. This motivates investigation on Formal Model Based
Design approaches for automatic synthesis of SBCS control software. In previous
works we presented an algorithm, along with a tool QKS implementing it, that
from a formal model (as a Discrete Time Linear Hybrid System, DTLHS) of the
controlled system (plant), implementation specifications (that is, number of
bits in the Analog-to-Digital, AD, conversion) and System Level Formal
Specifications (that is, safety and liveness requirements for the closed loop
system) returns correct-by-construction control software that has a Worst Case
Execution Time (WCET) linear in the number of AD bits and meets the given
specifications. In this technical report we present full experimental results
on using it to synthesize control software for two versions of buck DC-DC
converters (single-input and multi-input), a widely used mixed-mode analog
circuit.Comment: arXiv admin note: text overlap with arXiv:1107.563
Parallel statistical model checking for safety verification in smart grids
By using small computing devices deployed at user premises, Autonomous Demand Response (ADR) adapts users electricity consumption to given time-dependent electricity tariffs. This allows end-users to save on their electricity bill and Distribution System Operators to optimise (through suitable time-dependent tariffs) management of the electric grid by avoiding demand peaks.
Unfortunately, even with ADR, users power consumption may deviate from the expected (minimum cost) one, e.g., because ADR devices fail to correctly forecast energy needs at user premises. As a result, the aggregated power demand may present undesirable peaks.
In this paper we address such a problem by presenting methods and a software tool (APD-Analyser) implementing them, enabling Distribution System Operators to effectively verify that a given time-dependent electricity tariff achieves the desired goals even when end-users deviate from their expected behaviour.
We show feasibility of the proposed approach through a realistic scenario from a medium voltage Danish distribution network
User flexibility aware price policy synthesis for smart grids
In order to optimally manage a modern electricity distribution network, peaks in residential users demand should be avoided, as this can reduce energy and network asset management costs. Furthermore, this must be done without compressing residential users demand. To this aim, in a demand response setting, residential users are given a price policy, which economically motivates them to shift their loads in order to achieve this goal. However, if the price policy for all users is similar, this demand response may result in simply shifting the demand peaks (peak rebound), leaving the problem unsolved. In this paper we propose a novel methodology which i) for each network substation s, automatically computes the desired power profile to be kept in order to optimally manage the network itself, ii) for each network substation s, automatically synthesizes individualized price policies for residential users connected to s, so that s is kept at the desired profile. Note that price policies individualization avoids the peak rebound problem, as different users have different low tariff areas. Furthermore, our methodology measures the flexibility of a residential user as the capacity needed by a home energy storage system (e.g., a battery) to always follow the given price policy, thus mitigating residential users discomfort. We show the feasibility of our approach on a realistic scenario taken from an existing medium voltage Danish distribution network
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