142 research outputs found
Variations of model checking
The logic ATCTL is a convenient logic to specify properties with actions and real-time. It is intended as a property language for Lightweight UML models [12], which consist mainly of simplified class diagrams and statecharts. ATCTL combines two known extensions of CTL, namely ACTL and TCTL. The reason to extend CTL with both actions and real time is that in LUML state¿transition diagrams, we specify states, actions and real time, and our properties refer to all of these elements. The analyst therefore needs a property language that contains constructs for all these elements. ATCTL can be reduced to ACTL as well as to TCTL, and therefore also to CTL. This gives us a choice of tools for model checking; we have used is Kronos [13], a TCTL model checker
Achieving Cost-Effective Software Reliability Through Self-Healing
Heterogeneity, mobility, complexity and new application domains raise new software reliability issues that cannot be met cost-effectively only with classic software engineering approaches. Self-healing systems can successfully address these problems, thus increasing software reliability while reducing maintenance costs. Self-healing systems must be able to automatically identify runtime failures, locate faults, and find a way to bring the system back to an acceptable behavior. This paper discusses the challenges underlying the construction of self-healing systems with particular focus on functional failures, and presents a set of techniques to build software systems that can automatically heal such failures. It introduces techniques to automatically derive assertions to effectively detect functional failures, locate the faults underlying the failures, and identify sequences of actions alternative to the failing sequence to bring the system back to an acceptable behavior
ONTOLOGY-ENABLED TRACEABILITY MODELS FOR ENGINEERING SYSTEMS DESIGN AND MANAGEMENT
This thesis describes new models and a system for satisfying requirements, and an architectural framework for linking discipline-specific dependencies through inter- action relationships at the ontology (or meta-model) level. In a departure from state-of-the-art traceability mechanisms, we ask the question: What design concept (or family of design concepts) should be applied to satisfy this requirement? Solu- tions to this question establish links between requirements and design concepts. The implementation of these concepts leads to the design itself. These ideas, and support for design-rule checking are prototyped through a series of progressively complicated applications, culminating in a case study for rail transit systems management
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Extension of early stage failure analysis tools to Prognostics Health Management design
Modern complex mechanical systems have evolved to a point of incredible complexity. Many now operate with significant assistance from automated response functions, and some operate without human operators at all. These increasingly complex systems have also become more expensive and more ambitions in mission, bringing about higher risk to both money and life. In
response to these risks, Prognostics and Health Management (PHM) systems are developed to detect, manage, notify, mitigate, and respond to the potential failures in these high risk complex systems. The responsibilities carried by PHM systems make them as integral to the successful operation of a complex machine as any other major system. While methods have been developed and are in use to consider risk and reliability in the early stage of complex system design, explicit consideration of PHM capability and architecture are often left for later stages in the design process. In this work, several risk and reliability based design techniques are discussed with consideration of PHM development. In particular, the Function Failure Identification Propagation
(FFIP) framework provides a systematic process to identify potential failure points and the resulting functional losses from a model based architecture. Research into PHM and embedded system co-design indicates that FFIP is a good starting point for early stage PHM architecture development. In this body, FFIP is first augmented to more completely capture the data needed for preliminary PHM architecture and to begin to address PHM capability in early stage complex system design. Second, an embedded systems design process centered around StateCharts is developed for specific application to the FFIP process in order to facilitate PHM system design during early stage complex system design
Nobody’s perfect: interactive synthesis from parametrized real-time scenarios
ABSTRACT As technical systems keep growing more complex and sophisticated, designing software for the safety-critical coordination between their components becomes increasingly difficult. Verifying and correcting these components already represents a significant part of the development process both with respect to time and cost. Scenario-based synthesis has been put forward as an approach to accelerate the transition from requirements to a correct, verified model. I
Semantics and Verification of UML Activity Diagrams for Workflow Modelling
This thesis defines a formal semantics for UML activity diagrams that is suitable for workflow modelling. The semantics allows verification of functional requirements using model checking. Since a workflow specification prescribes how a workflow system behaves, the semantics is defined and motivated in terms of workflow systems. As workflow systems are reactive and coordinate activities, the defined semantics reflects these aspects. In fact, two formal semantics are defined, which are completely different. Both semantics are defined directly in terms of activity diagrams and not by a mapping of activity diagrams to some existing formal notation. The requirements-level semantics, based on the Statemate semantics of statecharts, assumes that workflow systems are infinitely fast w.r.t. their environment and react immediately to input events (this assumption is called the perfect synchrony hypothesis). The implementation-level semantics, based on the UML semantics of statecharts, does not make this assumption. Due to the perfect synchrony hypothesis, the requirements-level semantics is unrealistic, but easy to use for verification. On the other hand, the implementation-level semantics is realistic, but difficult to use for verification. A class of activity diagrams and a class of functional requirements is identified for which the outcome of the verification does not depend upon the particular semantics being used, i.e., both semantics give the same result. For such activity diagrams and such functional requirements, the requirements-level semantics is as realistic as the implementation-level semantics, even though the requirements-level semantics makes the perfect synchrony hypothesis. The requirements-level semantics has been implemented in a verification tool. The tool interfaces with a model checker by translating an activity diagram into an input for a model checker according to the requirements-level semantics. The model checker checks the desired functional requirement against the input model. If the model checker returns a counterexample, the tool translates this counterexample back into the activity diagram by highlighting a path corresponding to the counterexample. The tool supports verification of workflow models that have event-driven behaviour, data, real time, and loops. Only model checkers supporting strong fairness model checking turn out to be useful. The feasibility of the approach is demonstrated by using the tool to verify some real-life workflow models
Colored model based testing for software product lines (CMBT-SWPL)
Over the last decade, the software product line domain has emerged as
one of the mostpromising software development paradigms. The main benefits
of a software product lineapproach are improvements in productivity, time
to market, product quality, and customersatisfaction.Therefore, one topic
that needs greater emphasis is testing of software product lines toachieve
the required software quality assurance. Our concern is how to test a
softwareproduct line as early as possible in order to detect errors,
because the cost of error detectedIn early phases is much less compared to
the cost of errors when detected later.The method suggested in this thesis
is a model-based, reuse-oriented test technique calledColored Model Based
Testing for Software Product Lines (CMBT-SWPL). CMBT-SWPLis a
requirements-based approach for efficiently generating tests for products
in a soft-ware product line. This testing approach is used for validation
and verification of productlines. It is a novel approach to test product
lines using a Colored State Chart (CSC), whichconsiders variability early
in the product line development process. More precisely, the vari-ability
will be introduced in the main components of the CSC. Accordingly, the
variabilityis preserved in test cases, as they are generated from colored
test models automatically.During domain engineering, the CSC is derived
from the feature model. By coloring theState Chart, the behavior of
several product line variants can be modeled simultaneouslyin a single
diagram and thus address product line variability early. The CSC
representsthe test model, from which test cases using statistical testing
are derived.During application engineering, these colored test models are
customized for a specificapplication of the product line. At the end of
this test process, the test cases are generatedagain using statistical
testing, executed and the test results are ready for evaluation.
Inxaddition, the CSC will be transformed to a Colored Petri Net (CPN) for
verification andsimulation purposes.The main gains of applying the
CMBT-SWPL method are early detection of defects inrequirements, such as
ambiguities incompleteness and redundancy which is then reflectedin saving
the test effort, time, development and maintenance costs
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