The increasing complexity of reactive systems can be mitigated with the use of components and composition languages in model-driven engineering. Designing composition languages is a challenge itself as both practical applicability (support for different composition approaches in various application domains), and precise formal semantics (support for verification and code generation) have to be taken into account. In our Gamma Statechart Composition Framework, we designed and implemented a composition language for the synchronous, cascade synchronous and asynchronous composition of statechart-based reactive components. We formalized the semantics of this composition language that provides the basis for generating composition-related Java source code as well as mapping the composite system to a back-end model checker for formal verification and model-based test case generation. In this paper, we present the composition language with its formal semantics, putting special emphasis on design decisions related to the language and their effects on verifiability and applicability. Furthermore, we demonstrate the design and verification functionality of the composition framework by presenting case studies from the cyber-physical system domain.

The Gamma Statechart Composition Framework is an integrated tool to support the design, verification and validation as well as code generation for component-based reactive systems. The behavior of each component is captured by a statechart, while assembling the system from components is driven by a domain-specific composition language. Gamma automatically synthesizes executable Java code extending the output of existing statechart-based code generators with composition related parts, and it supports formal verification by mapping composite statecharts to a back-end model checker. Execution traces obtained as witnesses during verification are back-annotated as test cases to replay an error trace or to validate external code generators. Tool demonstration video: https://youtu.be/ng7lKd1wlDo CCS CONCEPTS • Theory of computation → Verification by model checking; • Software and its engineering → System modeling languages; Formal software verification;

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Software-intensive distributed controllers are becoming increasingly prevalent, among others, also in railway interlocking systems (RIS). As such systems carry out critical tasks, their systematic verification and testing are a must, which can be supported by formal methods. This paper presents a verification and testing approach for a distributed RIS subsystem using hidden formal methods. The subsystem's functional behavior is modeled using statechart components defined in a high-level UML-based modeling language, which are integrated according to sound execution and interaction semantics defined by the RIS protocol. The emergent model is automatically mapped into input formalisms of model checker back-ends. Integration tests for the system implementation are derived according to various modelbased coverage criteria using the model checker back-ends and generated properties. The approach is implemented in our open source Gamma Statechart Composition Framework.

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Control systems are typically tightly embedded into their environment to enable adaptation to environmental effects. As the complexity of such adaptive systems is rapidly increasing, there is a strong need for coherent tool‐centric approaches to aid their systematic development. This paper proposes an end‐to‐end component‐based specification, design and verification approach for adaptive systems based on the integration of a high‐level scenario language (sequence chart variant) and an adaptation definition language (statechart extension) in the open source Gamma tool. The scenario language supports high‐level constructs for specifying contracts and the adaptation definition language supports the flexible activation and deactivation of static contracts and managed elements (state‐based components) based on internal changes (e.g., faults), environmental changes (e.g., varying context) or interactions. The approach supports linking managed elements to static contracts to formally verify their adherence to the specified behavior at design time using integrated model checkers. Implementation can be derived from the adaptation model automatically, which can be tested using automated test generation and verified at runtime by contract‐based monitors.

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