417,264 research outputs found
Formal Model Engineering for Embedded Systems Using Real-Time Maude
This paper motivates why Real-Time Maude should be well suited to provide a
formal semantics and formal analysis capabilities to modeling languages for
embedded systems. One can then use the code generation facilities of the tools
for the modeling languages to automatically synthesize Real-Time Maude
verification models from design models, enabling a formal model engineering
process that combines the convenience of modeling using an informal but
intuitive modeling language with formal verification. We give a brief overview
six fairly different modeling formalisms for which Real-Time Maude has provided
the formal semantics and (possibly) formal analysis. These models include
behavioral subsets of the avionics modeling standard AADL, Ptolemy II
discrete-event models, two EMF-based timed model transformation systems, and a
modeling language for handset software.Comment: In Proceedings AMMSE 2011, arXiv:1106.596
A temporal logic for the specification and verification of real-time systems
The development of a product typically starts with the specification of the user’s requirements and ends with the design of a system to meet those requirements. Traditional approaches to the specification and analysis of a system abstracted away from any notion of time at the specification level. However, for a real-time system the specification may include timing requirements. Many specification and verification methods for real-time systems are based on the assumption that time is discrete because the verification methods using it are significantly simpler than those using continuous time. Yet real-time systems operate in ‘real’ continuous time and their requirements are often specified using a continuous time model.
In this thesis we develop a temporal logic and proof methods for the specification and verification of a real-time system which can be applied irrespective of whether time is discrete, continuous or dense. The logic is based on the definition of the next operator as the next time point a change in state occurs or if no state change occurs then it is the time point obtained by incrementing the current time by one. We show that this definition of the next operator leads to a logic which is expressive enough for specifying real-time systems where continuous time is required, and in which the verification and proof methods developed for discrete time can be used. To demonstrate the applicability of the logic several varied examples including communication protocols and digital circuits are specified and their real-time properties proved. A compositional proof system which supports hierarchical development of programs is also developed for a real-time extension of a CSP-like language
Timed Runtime Monitoring for Multiparty Conversations
We propose a dynamic verification framework for protocols in real-time distributed systems. The framework is based on Scribble, a tool-chain for design and verification of choreographies based on multiparty session types, developed with our industrial partners. Drawing from recent work on multiparty session types for real-time interactions, we extend Scribble with clocks, resets, and clock predicates constraining the times in which interactions should occur. We present a timed API for Python to program distributed implementations of Scribble specifications. A dynamic verification framework ensures the safe execution of applications written with our timed API: we have implemented dedicated runtime monitors that check that each interaction occurs at a correct timing with respect to the corresponding Scribble specification. The performance of our implementation and its practicability are analysed via benchmarking
Formalization and Correctness of the PALS Architectural Pattern for Distributed Real-Time Systems
Many Distributed Real-Time Systems (DRTS), such as integrated modular avionics systems and distributed control systems in
motor vehicles, are made up of a collection of components communicating asynchronously among themselves and with their environment
that must change their state and respond to environment inputs within
hard real-time bounds. Such systems are often safety-critical and need
to be certi???ed; but their certi???cation is currently very hard due to their
distributed nature. The Physically Asynchronous Logically Synchronous
(PALS) architectural pattern can greatly reduce the design and veri???cation complexities of achieving virtual synchrony in a DTRS. This work
presents a formal speci???cation of PALS as a formal model transformation that maps a synchronous design, together with a set of performance
bounds of the underlying infrastructure, to a formal DRTS speci???cation
that is semantically equivalent to the synchronous design. This semantic
equivalence is proved, showing that the formal veri???cation of temporal
logic properties of the DRTS can be reduced to their veri???cation on the
much simpler synchronous design. An avionics system case study is used
to illustrate the usefulness of PALS for formal verification purposes.unpublishednot peer reviewe
Verification and Optimization of a PLC Control Schedule
We report on the use of the SPIN model checker for both the verification of a process control program and the derivation of optimal control schedules. This work was carried out as part of a case study for the EC VHS project (Verification of Hybrid Systems), in which the program for a Programmable Logic Controller (PLC) of an experimental chemical plant had to be designed and verified. The intention of our approach was to see how much could be achieved here using the standard model checking environment of SPIN/Promela. As the symbolic calculations of real-time model checkers can be quite expensive it is interesting to try and exploit the efficiency of established non-real-time model checkers like SPIN in those cases where promising work-arounds seem to exist. In our case we handled the relevant real-time properties of the PLC controller using a time-abstraction technique; for the scheduling we implemented in Promela a so-called variable time advance procedure. For this case study these techniques proved sufficient to verify the design of the controller and derive (time-)optimal schedules with reasonable time and space requirements
PALS-Based Analysis of an Airplane Multirate Control System in Real-Time Maude
Distributed cyber-physical systems (DCPS) are pervasive in areas such as
aeronautics and ground transportation systems, including the case of
distributed hybrid systems. DCPS design and verification is quite challenging
because of asynchronous communication, network delays, and clock skews.
Furthermore, their model checking verification typically becomes unfeasible due
to the huge state space explosion caused by the system's concurrency. The PALS
("physically asynchronous, logically synchronous") methodology has been
proposed to reduce the design and verification of a DCPS to the much simpler
task of designing and verifying its underlying synchronous version. The
original PALS methodology assumes a single logical period, but Multirate PALS
extends it to deal with multirate DCPS in which components may operate with
different logical periods. This paper shows how Multirate PALS can be applied
to formally verify a nontrivial multirate DCPS. We use Real-Time Maude to
formally specify a multirate distributed hybrid system consisting of an
airplane maneuvered by a pilot who turns the airplane according to a specified
angle through a distributed control system. Our formal analysis revealed that
the original design was ineffective in achieving a smooth turning maneuver, and
led to a redesign of the system that satisfies the desired correctness
properties. This shows that the Multirate PALS methodology is not only
effective for formal DCPS verification, but can also be used effectively in the
DCPS design process, even before properties are verified.Comment: In Proceedings FTSCS 2012, arXiv:1212.657
From AADL Model to LNT Specification
The verification of distributed real-time systems designed by architectural languages such as AADL (Architecture Analysis and Design Language) is a research challenge. These systems are often used in safety- critical domains where one mistake can result in physical damages and even life loss. In such domains, formal methods are a suitable solution for rigorous analysis. This paper studies the formal verification of distributed real-time systems modelled with AADL. We transform AADL model to another specification formalism enabling the verification. We choose LNT language which is an input to CADP toolbox for formal analysis. Then, we illustrate our approach with the ”Flight Control System” case study
TURTLE: Four Weddings and a Tutorial
The paper discusses an educational case study of protocol modelling in TURTLE, a real-time UML profile supported by the open source toolkit TTool. The method associated with TURTLE is step by step illustrated with the connection set up and handover procedures defined for the Future Air navigation Systems. The paper covers the following methodological stages: requirement modeling, use-case driven and scenario based analysis, object-oriented design and rapid prototyping in Java. Emphasis is laid on the formal verification of analysis and design diagrams
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