vaida-abstract
Abstract - lic thesis David Broman
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Safety, Security, and Semantic Aspects of Equation-Based
Object-Oriented Languages and Environments
Abstract:
During the last two decades, the interest for computer aided
modeling and simulation of complex physical systems has witnessed a
significant growth. The recent possibility to create acausal models,
using components from different domains (e.g., electrical, mechanical,
and hydraulic) enables new opportunities. Modelica is one of the most
prominent equation-based object-oriented (EOO) languages that support
such capabilities, including the ability to simulate both continuous-
and discrete-time models, as well as mixed hybrid models. However,
there are still many remaining challenges when it comes to language
safety and simulation security. The problem area concerns detecting
modeling errors at an early stage, so that faults can be isolated and
resolved. Furthermore, to give guarantees for the absence of faults in
models, the need for precise language specifications is vital, both
regarding type systems and dynamic semantics.
This thesis includes five papers related to these topics. The first
paper describes the informal concept of types in the Modelica language,
and proposes a new concrete syntax for more precise type definitions.
The second paper provides a new approach for detecting over- and
under-constrained systems of equations in EOO languages, based on a
concept called structural constraint delta. That approach makes use of
type checking and a type inference algorithm. The third paper outlines
a strategy for using abstract syntax as a middle-way between a formal
and informal language specification. The fourth paper suggests and
evaluates an approach for secure distributed co-simulation over wide
area networks. The final paper outlines a new formal operational
semantics for describing physical connections, which is based on the
untyped lambda calculus. A kernel language is defined, in which real
physical models are constructed and simulated.
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