Results 1 
4 of
4
Checking SCADE Models for Correct Usage of Physical Units
 Proc. of SAFECOMP'06, Sep. 2006, Gdansk/P, 358371; Springer LNCS
, 2006
"... Abstract. Mismatches of units and of scales of values in physical calculations are disastrous, but rather common, in the development of embedded control systems. They can be as plain as mixing feet and metres, or as hidden as a wrong exponent in a complex calculation formula. These errors can be fou ..."
Abstract

Cited by 5 (1 self)
 Add to MetaCart
Abstract. Mismatches of units and of scales of values in physical calculations are disastrous, but rather common, in the development of embedded control systems. They can be as plain as mixing feet and metres, or as hidden as a wrong exponent in a complex calculation formula. These errors can be found by a checking algorithm, following some simple rules, if information on the units of the used variables is provided. This paper describes a developer friendly approach of providing this checking functionality in SCADE, a modelbased graphical development tool for safetycritical embedded applications. 1 Key words: physical units, safety, verification, error detection, dependable embedded systems, model based software development, SCADE, DECOS 1
Inferring the context for evaluating physics algebraic equations when scaffolding is removed
 Proceedings of FLAIRS2004
, 2004
"... This paper describes our continuing work on enabling a tutor to evaluate algebraic solutions to word problems in physics. Current tutoring systems require students to explicitly define each variable that is used in the algebraic equations. We have developed a constraint propagation based heuristic a ..."
Abstract

Cited by 3 (2 self)
 Add to MetaCart
This paper describes our continuing work on enabling a tutor to evaluate algebraic solutions to word problems in physics. Current tutoring systems require students to explicitly define each variable that is used in the algebraic equations. We have developed a constraint propagation based heuristic algorithm that finds the possible dimensions and physics concepts for each variable. In earlier work we developed techniques that worked for a small set of problems and evaluated them on a small number of students. The work described here covers an extension to and evaluation of a much larger class of problems and a larger number of students. The results show that our technique uniquely determines the dimensions of all the variables in 89 % of the sets of equations. By asking the student for dimension information about one variable, an additional 3 % of the sets can be determined. Thus a physics tutoring system can use this technique to reason about a student’s answers even when the scaffolding and context are removed.
Checking for dimensional correctness in physics equations
 In Proceedings of Fourteenth International Florida AI Research Society Conference
, 2002
"... One of the key components of an Intelligent Tutoring System (ITS) is the mechanism for reasoning about the student’s input. The impact of this component extends far beyond the presentation of the lesson material to the success of the system itself. It affects how precisely the system can pinpoint st ..."
Abstract

Cited by 3 (2 self)
 Add to MetaCart
One of the key components of an Intelligent Tutoring System (ITS) is the mechanism for reasoning about the student’s input. The impact of this component extends far beyond the presentation of the lesson material to the success of the system itself. It affects how precisely the system can pinpoint student errors and thus the subsequent help that the system provides. This paper describes an example of a class of physics problems whose answers are most naturally represented as systems of algebraic equations. Analyzing such input requires not only an understanding of algebra but also knowledge of physics concepts. This paper describes a technique for determining the dimensional consistency of algebraic equations in physics using constraint propagation. Unlike other methods, it does not depend on the user defining the dimensions of each variable. Instead, it uses a knowledge base of well known physics variables combined with constraint propagation to determine both the dimensions of values (variables and constants) and also the dimensional consistency of an equation. The technique has been successfully tested on answers obtained from a class of college level introductory physics students.
Checking Data Flow Models for Correct Use of Physical Units
"... For developing embedded (control) software, graphical modeling languages based on the data flow paradigm are increasingly used, primarily due to the similarity with electronic (or electric, hydraulic etc.) circuit design. Here, software modules or functions, respectively, are essentially graphs with ..."
Abstract
 Add to MetaCart
For developing embedded (control) software, graphical modeling languages based on the data flow paradigm are increasingly used, primarily due to the similarity with electronic (or electric, hydraulic etc.) circuit design. Here, software modules or functions, respectively, are essentially graphs with nodes representing operations and edges representing signals (data). Signals often denote values of various physical units like current or voltage, but have to be represented by the same elementary signal (or data) type like "real", making automatic detection of mistakes like adding current and voltage or mixing feet and meters impossible at data type level. This paper describes how such errors can be detected in data flow computational models, keeping the additional workload for the model developer to a minimum. An example implementation for Simulink illustrates the usability of the taken approach, which is therefore an important means for verification of safetycritical software.