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

Extending the Real-Time Maude Semantics of Ptolemy to Hierarchical DE Models

This paper extends our Real-Time Maude formalization of the semantics of flat Ptolemy II discrete-event (DE) models to hierarchical models, including modal models. This is a challenging task that requires combining synchronous fixed-point computations with hierarchical structure. The synthesis of a Real-Time Maude verification model from a Ptolemy II DE model, and the formal verification of the synthesized model in Real-Time Maude, have been integrated into Ptolemy II, enabling a model-engineering process that combines the convenience of Ptolemy II DE modeling and simulation with formal verification in Real-Time Maude.Comment: In Proceedings RTRTS 2010, arXiv:1009.398

Applications and extensions of context-sensitive rewriting

[EN] Context-sensitive rewriting is a restriction of term rewriting which is obtained by imposing replacement restrictions on the arguments of function symbols. It has proven useful to analyze computational properties of programs written in sophisticated rewriting-based programming languages such asCafeOBJ, Haskell, Maude, OBJ*, etc. Also, a number of extensions(e.g., to conditional rewritingor constrained equational systems) and generalizations(e.g., controlled rewritingor forbidden patterns) of context-sensitive rewriting have been proposed. In this paper, we provide an overview of these applications and related issues. (C) 2021 Elsevier Inc. All rights reserved.Partially supported by the EU (FEDER), and projects RTI2018-094403-B-C32 and PROMETEO/2019/098.Lucas Alba, S. (2021). Applications and extensions of context-sensitive rewriting. Journal of Logical and Algebraic Methods in Programming. 121:1-33. https://doi.org/10.1016/j.jlamp.2021.10068013312

Twenty years of rewriting logic

AbstractRewriting logic is a simple computational logic that can naturally express both concurrent computation and logical deduction with great generality. This paper provides a gentle, intuitive introduction to its main ideas, as well as a survey of the work that many researchers have carried out over the last twenty years in advancing: (i) its foundations; (ii) its semantic framework and logical framework uses; (iii) its language implementations and its formal tools; and (iv) its many applications to automated deduction, software and hardware specification and verification, security, real-time and cyber-physical systems, probabilistic systems, bioinformatics and chemical systems

Operational analysis of sequence diagram specifications

This thesis is concerned with operational analysis of UML 2.x sequence diagram specifications. By operational analysis we mean analysis based on a characterization of the executions of sequence diagrams, or in other words an operational semantics for sequence diagrams. We define two methods for analysis of sequence diagram specifications – refinement verification and refinement testing – and both are implemented in an analysis tool we have named ‘Escalator’. Further, we make the first steps in the direction of extending our approach with support for availability analysis. In order to facilitate operational analysis, we define an operational semantics for UML 2.x sequence diagrams. The operational semantics is loyal to the intended semantics of UML, and is proven to be sound and complete with respect to the denotational semantics for sequence diagrams defined in STAIRS – a framework for stepwise development based on refinement of sequence diagram specifications. The operational semantics has a formalized meta-level, on which we define execution strategies. This meta-level allows us to make distinctions between positive and negative behavior, between potential and universal behavior, and between potential and mandatory choice, all of which are inherently difficult in an operational semantics. Based on the operational semantics and its formalized meta-level, we define trace generation, test generation and test execution. Further, based on a formalization of refinement in STAIRS, the trace generation is used to devise a method for refinement verification, and the test generation and the test execution are used to define a method for refinement testing. Both are methods for investigating whether or not a sequence diagram specification is a correct refinement of another sequence diagram specification. The operational semantics, the refinement verification and the refinement testing are implemented with the term rewriting language Maude, and these implementations are integrated in the Escalator tool. In addition, Escalator provides a graphical user interface for working with sequence diagram specifications and for running the analyses. In order to facilitate availability analysis, we define a conceptual model for service availability where the basic properties of availability are identified. Further, we extend the operational semantics with support for one class of these basic properties, namely real-time properties, and outline how the operation semantics extended with time can be applied to make methods for timed analysis of sequence diagram specifications

www.elsevier.com/locate/entcs Real-Time Maude 2.1

Real-Time Maude 2.1 is an extension of Full Maude 2.1 supporting the formal specification and analysis of real-time and hybrid systems. Symbolic simulation, search and model checking analysis are supported for a wide range of systems. This paper gives an overview of the tool and documents its semantic foundations