| Today's complex cyber-physical systems (CPSs) are created using models throughout the system development life cycle, a process referred to as model-based design (MBD). The
heterogeneity of elements in CPSs requires multiple perspectives and formalisms to explore
the complete design space. Ensuring the consistency of these various system models is an
important part of the integrated MBD approach.
In this thesis, we propose to unify heterogeneous system models through light-weight
representations of their structure and semantics using architectural descriptions. Architectures are annotated structural representations that describe systems at a high level of
abstraction, allowing designers to determine appropriate assignment of functionality to
elements, and make trade-o s between different quality attributes. There are two fundamental shortcomings of current architecture modeling capabilities that limit their potential
to fully address the engineering problems of large-scale, heterogeneous CPSs: (i) limited
vocabulary to represent physical elements and their interactions; and (ii) inadequate ways
to support consistency relations between heterogeneous architecture views of the same
system.
This thesis addresses the first shortcoming through the development of the CPS architectural style that supports a uni ed representation of both physical and cyber elements
and their interactions in the same framework. This ability allows the architect to create
a common base architecture (BA) for a CPS that provides a uni ed point of reference for
multi-domain system models. To address the second shortcoming, the architectural view is
used as the mechanism to represent the architectures of system models as abstractions of
the underlying shared BA. In this context, well-de ned mappings between a view and the
BA are used to identify and manage semantically equivalent elements (and their relations)
between each model and the underlying system.
Structural consistency de nes when an architectural view conforms to the structural and
semantic constraints imposed by components and connectors in the system's BA. Such a
notion of consistency ensures that the model elements adhere to the connectivity constraints
and physical laws present between elements in the BA. We define view consistency as the
existence of an appropriate morphism between the typed graphs of a view and the BA.
Depending on the type of morphism present, two notions of consistency are defined: view
conformance and view completeness.
Our tool framework is implemented in the AcmeStudio architecture design framework,
and consists of a view map language, a graphical view editor, and a set of graph morphism
algorithms for consistency checking. We illustrate the application of our architectural
approach with two case studies: an autonomous quadrotor with heterogeneous legacy
models, and management of model variants in simulation environments for engine control
of vehicles. |
