Evaluate emergent behaviour

Description

This solution method allows the designer to evaluate the effects of emergent behaviours on the SoS. The analysis consists in the identification, discovery and quantification of emergence. The results that are obtained highlight the conditions under which emergence takes place, its likelihood, and the kind of expected or unexpected effects due to emergence. Different methods need to be employed depending on the nature of the emergent property to be evaluated.

Initial Situation

The Constituent Systems must have been modelled behaviourally, and the structure of the SoS must have been specified. If required, a model of the emergent behaviours of interest must have been developed in the form of global parameters or GCSL assertions. Operational scenarios must also be available if the evaluation is used to identify implied scenarios. When dealing with emergence due to dynamicity, a Graph Grammar specification must be developed, and various alternative architectures must be made available.

Expected Result

A successful evaluation provides confirmation or denial of known emergent behaviours against time. The method is also able to help with the discovery of previously unknown or unexpected emergent behaviours.

Required Tools

The evaluation of emergent behaviours involves the use of most of the DANSE tools, depending on the particular alternative evaluation methods. The tools required for this activity include IBM Rhapsody for the specification of the system, GCSL for the specification of assertions, other potentially external tools for the specification of the system behaviour, DESYRE to perform the system simulation, and PLASMA to evaluate the likelihood of satisfaction of the assertions. Tool-Net must be used to coordinate the use of the other tools. The DANSE tools are required in particular to evaluate emergence in the presence of dynamicity specified through Graph Grammars, and in the process of designing emergence, through concise modelling and architecture optimisation.

·         Rhapsody, with FMU export, Dymola, Modelica

·         System Architect

·         Architecture patterns

·         Architecture generation

·         DANSE modelling extensions profiles

·         GCSL editor

·         Abstraction tools

·         Architecture Optimization Workbench

·         DESYRE

·         PLASMA

·         Tool-Net

Figure 54: Tool Flow: Evaluate Emergent Behaviour

Activities

A list of activities and activity diagrams for different approaches to evaluate emergent behaviours are shown in this deliverable in Section 4.6.1

Limitations

The evaluation of emergent behaviour is generally subject to the experience of the designer or domain expert, who must provide input regarding the effective emergent nature of the behaviours observed during simulation. In general, the evaluation of emergent behaviour rests on the ability to run an accurate simulation of the SoS: thus, this solution method inherits all the limitations of joint simulation. In particular, the models must be faithful abstractions of the real system. Even in this case, since abstraction is required for acceptable performance, the simulation may deviate from the actual execution of a system. Non-determinism and non-linearities may prevent or favour the emergence of behaviours.

Follow-up Solution Methods

The evaluation of emergence may be followed by methods intended to correct or to optimise the system performance in relation to the detected behaviours. This may include the evaluation of goals and contracts, to verify that the system satisfies its requirements. Similarly, it may include the generation of new architectural alternatives, or the application or architecture patterns, in order to favour or disable the emergence of certain behaviours.
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