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Determining Over- and Under-Constrained Systems of Equations using Structural Constraint Delta
Linköping University, Department of Computer and Information Science. (PELAB)
Linköping University, Department of Computer and Information Science. (PELAB)
Linköping University, Department of Computer and Information Science. (PELAB)ORCID iD: 0000-0002-3435-4996
2006 (English)Conference paper, Published paper (Other academic)
Abstract [en]

Computer aided modeling and simulation of complex physical systems, using components from multiple application domains, such as electrical, mechanical, and hydraulic, have in recent years witnessed a significant growth of interest. In the last decade, equation-based object-oriented (EOO) modeling languages, (e.g. Modelica, gPROMS, and VHDL-AMS) based on acausal modeling using Differential Algebraic Equations (DAEs), have appeared. With such languages, it is possible to model physical systems at a high level of abstraction by using reusable components.A model in an EOO language needs to have the same number of equations as unknowns. A previously unsolved problem concerning this property is the efficient detection of over- or under-constrained models in the case of separately compiled models.This paper describes a novel technique to determine over- and under-constrained systems of equations in models, based on a concept called structural constraint delta. In many cases it is also possible to locate the source of the constraint-problem. Our approach makes use of static type checking and consists of a type inference algorithm. We have implemented it for a subset of the Modelica language, and successfully validated it on several examples.

Place, publisher, year, edition, pages
2006. 151-160 p.
Keyword [en]
equation-based, modeling, object-oriented, over-constrained, separate compilation, type checking, under-constrained, simulation languages, algorithms
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-12699DOI: 10.1145/1173706.1173729OAI: oai:DiVA.org:liu-12699DiVA: diva2:16878
Conference
Proceedings of the 5th International Conference on Generative Programming and Component Engineering
Available from: 2007-11-16 Created: 2007-11-16 Last updated: 2014-10-08
In thesis
1. Safety, Security, and Semantic Aspects of Equation-Based Object-Oriented Languages and Environments
Open this publication in new window or tab >>Safety, Security, and Semantic Aspects of Equation-Based Object-Oriented Languages and Environments
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Institutionen för datavetenskap, 2007. 26 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1337
Keyword
Modeling, Simulation, Equation-Based, Object-Oriented, Modelica, Type System, Semantics, Language Safety, Secure Simulation
National Category
Computer Science
Identifiers
urn:nbn:se:liu:diva-10134 (URN)978-91-85895-24-3 (ISBN)
Presentation
2007-12-07, Visionen, B, Linköpings universistet, Linköping, 13:15 (English)
Opponent
Supervisors
Note
Report code: LIU-TEK-LIC-2007:46. On the day of the defence date the status of article IV was: In Progress; The status of article V was: Manuscript.Available from: 2007-11-16 Created: 2007-11-16 Last updated: 2014-10-08

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Broman, DavidNyström, KajFritzson, Peter

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