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Event Entry
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What and Who
Semantics of model composition in the Chi language
Georgina Fabian
Technische Universitaet Eindhoven
Talk
AG 1, AG 2, AG 3, AG 4
AG Audience
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Date, Time and Location
Friday, 16 July 99
14:00
60 Minutes
46.1 - MPII
022
Saarbrücken
Abstract
The objective of this talk is to present the hybrid Chi language, and specifically, to focus on model composition in Chi.
The Chi language is a hybrid specification language, suitable for the description of discrete-event, continuous-time, and hybrid systems. It is a concurrent language, where the discrete-event part is based on Communicating Sequential Processes (CSP) and the continuous part is based on Differential Algebraic Equations.
A Chi model consists of a set of processes running concurrently, each having a discrete and/or a continous specification part. Events are specified using event statements in the discrete-event part of the processes. Model composition is realized by connecting processes by channels and grouping them into systems. Channels connect pairs of processes. Discrete channels are used for point-to-point synchronous data communication as in CSP. Continuous channels connect pairs of continous variables and establish an equality relation among them.
How equality is ensured among connected continuous variables is a significant question. Possible connection semantics that are used in today's hybrid languages are: shared variables, causal connections and algebraic equations. These possibilities will be evaluated during the presentation. Model composition is determined in Chi by the following four factors:
1. Connected continuous variables define algebraic equations.
2. Only local variables are allowed.
3. Differential and algebraic variables are distinguished. Only the values of differential variables can be freely
chosen.
4. After discontinuity, a consistent continuous state is calculated only when all processes are finished with their
discrete-event actions.
These four factors together determine a robust and elegant model composition that will be demonstrated by examples.
The Chi language is a hybrid specification language, suitable for the description of discrete-event, continuous-time, and hybrid systems. It is a concurrent language, where the discrete-event part is based on Communicating Sequential Processes (CSP) and the continuous part is based on Differential Algebraic Equations.
A Chi model consists of a set of processes running concurrently, each having a discrete and/or a continous specification part. Events are specified using event statements in the discrete-event part of the processes. Model composition is realized by connecting processes by channels and grouping them into systems. Channels connect pairs of processes. Discrete channels are used for point-to-point synchronous data communication as in CSP. Continuous channels connect pairs of continous variables and establish an equality relation among them.
How equality is ensured among connected continuous variables is a significant question. Possible connection semantics that are used in today's hybrid languages are: shared variables, causal connections and algebraic equations. These possibilities will be evaluated during the presentation. Model composition is determined in Chi by the following four factors:
1. Connected continuous variables define algebraic equations.
2. Only local variables are allowed.
3. Differential and algebraic variables are distinguished. Only the values of differential variables can be freely
chosen.
4. After discontinuity, a consistent continuous state is calculated only when all processes are finished with their
discrete-event actions.
These four factors together determine a robust and elegant model composition that will be demonstrated by examples.
Contact
Tom Henzinger
301
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Tags, Category, Keywords and additional notes
Chi language