Pierre de Saqui-Sannes

TEPE: a SysML language for time-constrained property modeling and formal verification

Using UML or SysML models in a verification-centric method requires a property expression language, a formal semantics, and a tool. The paper introduces TEPE, a graphical TEmporal Property Expression language based on SysML parametric diagrams. TEPE enriches the expressiveness of other common property languages in particular with the notion of physical time and unordered signal reception. TEPE is further instantiated in the AVATAR real-time UML profile. TTool, an open-source toolkit, implements a press-button approach for the formal verification of AVATAR-TEPE properties with UPPAAL. An elevator system serves as example

Testing Real-Time Systems Using TINA

The paper presents a technique for model-based black-box conformance testing of real-time systems using the Time Petri Net Analyzer TINA. Such test suites are derived from a prioritized time Petri net composed of two concurrent sub-nets specifying respectively the expected behaviour of the system under test and its environment.We describe how the toolbox TINA has been extended to support automatic generation of time-optimal test suites. The result is optimal in the sense that the set of test cases in the test suite have the shortest possible accumulated time to be executed. Input/output conformance serves as the notion of implementation correctness, essentially timed trace inclusion taking environment assumptions into account. Test cases selection is based either on using manually formulated test purposes or automatically from various coverage criteria specifying structural criteria of the model to be fulfilled by the test suite. We discuss how test purposes and coverage criterion are specified in the linear temporal logic SE-LTL, derive test sequences, and assign verdicts.

Static analysis techniques to verify mutual exclusion situations within SysML models

AVATAR is a real-time extension of SysML supported by the TTool open-source toolkit. So far, formal verification of AVATAR models has relied on reachability techniques that face a state explosion problem. The paper explores a new avenue: applying structural analysis to AVATAR models, so as to identify mutual exclusion situations. In practice, TTool translates a subset of an AVATAR model into a Petri net and solves an equation system built upon the incidence matrix of the net. TTool implements a push-button approach and displays verification results at the AVATAR model level. The approach is not restricted to AVATAR and may be adapted to other UML profiles.

Adding a methodological assistant to a protocol modeling environment

The use of protocol design toolkits based on UML profiles has been hampered by the lack of methodological support. Indeed, those toolkits should include an assistant based on patterns and dedicated to driving the designer step by step through a well defined methodology. Thus, the TURTLE UML profile is extended with widely accepted service and protocol-oriented patterns. These patterns are built upon UML analysis diagrams i.e. use case, interaction overview and sequence diagrams. Moreover, all these patterns and diagrams have a formal semantics. Finally, they have been implemented in TTool, the open-source toolkit supporting TURTLE. The proposed approach remains general and may be applied to various modeling languages and use-case analysis driven processes.

SysML modeling for embedded systems design optimization: A case study

Model-Based Systems Engineering (MBSE) with the SysML language allows the designer to include requirement capture and design representation in a single model. This paper proposes a methodology to obtain the best design alternative, from a SysML design, by using multi-objective optimization techniques. A SysML model is extended with stereotypes, objective functions, variability and constraints. Then an integer representation of the problem can be generated and solved as a constraint satisfaction problem (CSP). The paper illustrates our methodology using an Embedded Cognitive Safety System (ECSS) design. From a component repository and redundancy alternatives, the best design alternatives are generated, to minimize the total cost and maximize the estimated system reliability.

Multi domain optimization with SysML modeling

Finding the set of optimal architectures is an important challenge for the designer who uses the Model-Based System Engineering with SysML. The paper discusses the application of techniques to solve a Constraint Satisfaction Multi-criteria Optimization Problem (CSMOP) obtained from a SysML model. In this paper, we present our methodology and propose several stereotypes for model variability, including continuous and discrete variables. Then we define a new parametric diagram usage for context modeling optimization. From this optimization context and model variability, it is possible to generate a problem description file for the PyOpt optimization framework. Finally a case study combining optical and electronic parameters illustrates the methodology with numerical results.

Time-Optimal Real-Time Test Case Generation Using Prioritized Time Petri Nets

This paper discusses the application of modelchecking to test generation from specifications written inPrioritized Time Petri Nets. We demonstrate how toautomatically generate conformance test cases, specially timedtest cases with optimal execution time, using the model checkerselt and the path analysis tool plan of the TINA toolbox.Properties are described in the SE-LTL temporal logic. Testcases are generated using manually formulated test purposesor automatically from various coverage criteria of the model.

Feasibility study of a multispectral camera with automatic processing onboard a 27U satellite using model based space system engineering

The paper discusses an experience in using SysML and the TTool software for the feasibility study of a novel multispectral camera for agricultural monitoring. Innovation lies in both automatic image processing onboard and mission control capabilities designed to comply with a 27U microsatellite. In addition to the mission accomplishment control, this innovative payload is capable of sending processed data directly to farms, critically reducing the delay between image making and its use in the field. This paper shows how MBSE and SysML may comply with phases 0 and A of a space project.

Architecture Optimization with SysML Modeling: A Case Study Using Variability

Obtaining the set of trade-off architectures from a SysML model is an important objective for the system designer. To achieve this goal, we propose a methodology combining SysML with the variability concept and multi-objectives optimization techniques. An initial SysML model is completed with variability information to show up the different alternatives for component redundancy and selection from a library. The constraints and objective functions are also added to the initial SysML model, with an optimization context. Then a representation of a constraint satisfaction problem (CSP) is generated with an algorithm from the optimization context and solved with an existing solver. The paper illustrates our methodology by designing an Embedded Cognitive Safety System (ECSS). From a component repository and redundancy alternatives, the best design alternatives are generated in order to minimize the total cost and maximize the estimated system reliability.

Conformance Testing of Preemptive Real-Time Systems

The paper presents an approach for model-based black-box conformance testing of preemptive real-time systems using Labeled Prioritized Time Petri Nets with Stopwatches LPrSwTPN. These models not only specify system/environment interactions and time constraints. They further enable modelling of suspend/resume operations in real-time systems. The test specification used to generate test primitives, to check the correctness of system responses and to draw test verdicts is an LPrSwTPN made up of two concurrent sub-nets that respectively specify the system under test and its environment. The algorithms used in the TINA model analyzer have been extended to support concurrent composed subnets. Relativized stopwatch timed input/output conformance serves as the notion of implementation correctness, essentially timed trace inclusion taking environment assumptions into account. Assuming the modelled systems are non deterministic and partially observable, the paper proposes a test generation and execution algorithm which is based on symbolic techniques and implements an online testing policy and outputs test results for the part of the selected environment.