Abstract Syntax Can Make the Definition of Modelica Less Abstract - - PowerPoint PPT Presentation

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Abstract Syntax Can Make the Definition of Modelica Less Abstract - - PowerPoint PPT Presentation

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Abstract Syntax Can Make the Definition of Modelica Less Abstract 1st International Workshop on Equation-Based Object-Oriented Languages and Tools Berlin July 30, 2007 David Broman and Peter Fritzson Linkping University, Sweden

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Linköping University David Broman, davbr@ida.liu.se

Abstract Syntax Can Make the Definition of Modelica Less Abstract

1st International Workshop on Equation-Based Object-Oriented Languages and Tools

Berlin July 30, 2007

David Broman and Peter Fritzson

Linköping University, Sweden {davbr,petfr}@ida.liu.se

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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Outline of the Talk

Part I - Why are specification improvements needed? Specification Goals and Problems Part II - What to specify? Transformation Aspect Rejection Aspect Part III - How to specify? Different Approaches Previous Attempts Abstract Syntax Approach

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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Part I Why are specification improvements needed?

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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Problem: Interpreting the specification

Modelica Language Specification Interpretation of syntax and semantics Simulation Tool

  • Dymola
  • Modelica System Designer
  • MOSILAB
  • SimulationX
  • OpenModelica

Problem

  • The Modelica Specification is open for interpretation
  • May result in incorrect and incompatible tools
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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Specification goals

Unambigious

"Can only be interpreted in exactly one way"

Expressive

"State the syntax and semantics in a compact manner"

Understandable

"Easy to grasp with moderate computer science knowledge"

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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Revolutionary Strategy Very large specification. Evolutionary Strategy. Abstract Syntax Approach

An evolutionary "middle-way" strategy

Informal approach

e.g. natural language text

Formal approach

e.g. operational semantics

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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Part II What to specify?

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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

What should be specified?

  • 1. Transformation Aspect

R=10 R L=1

L G Inertia1

J=0.1 E... k=1 sineVoltage spring c=1 bodyBox r={L1,0,0} b a a b n={0,0,1} revolute a b n={0,0,1} actuatedRev... bodyBox1 r={L2,0,0} b a

world

x y

Modelica Model Simulation Result

  • 2. Rejection Aspect

R=10 R L=1

L G Inertia1

J=0.1 E... k=1 sineVoltage spring c=1 bodyBox r={L1,0,0} b a a b n={0,0,1} revolute a b n={0,0,1} actuatedRev... bodyBox1 r={L2,0,0} b a

world

x y

Modelica Model

Syntax

  • the structure

Semantics

  • the meaning
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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Transformation Aspect

What is actually the result of an execution?

R=10 R L=1 L G Inertia1 J=0.1 E... k=1 sineVoltage spring c=1 bodyBox r={L1,0,0} b a a b n={0,0,1} revolute a b n={0,0,1} actuatedRev... bodyBox1 r={L2,0,0} b a world x y
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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Rejection Aspect

What is actually a valid Modelica model?

R=10 R L=1 L G Inertia1 J=0.1 E ... k=1 sineVoltage spring c=1 bodyBox r={L1,0,0} b a a b n={0,0,1} revolute a b n={0,0,1} actuatedRev... bodyBox1 r={L2,0,0} b a world x y
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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Part III How to specify?

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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Previous Specification Attempts

Informal approach

e.g. natural language text

Formal approach

e.g. operational semantics

RML and Natural Semantics

(Kågedal & Fritzson, 1998)

  • 1998, large subset of specfication
  • hard to get an overview of - became very large
  • now the code base for OpenModelica

Modelica Specification

(Modelica Association, 2005)

  • Informal semantics, natural language
  • Concrete syntax

Types in Modelica

(Broman, Fritzson & Furic, 2006)

  • Clarify the type concept in Modelica
  • Concerns only the rejection aspect

Instance Creation (Elaboration)

(Mauss, 2005)

  • Only transformation aspect
  • Subset of the language

Abstract Syntax Approach

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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Abstract Syntax as a Middle-Way Strategy

Scanning, Parsing => Abstract Syntax Tree (AST) Elaboration (transformation and rejection aspects)

  • Input: Implicitly specified using concrete syntax
  • Output: Not specified
  • Transformation: Informally specified using natural language
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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Transformation and Rejection Aspects

Transformation Aspect

  • Precise specification of input

and output (grammar)

  • Transformation still informal

Rejection Aspect

  • More restrictive than the concrete

syntax grammar

  • Include context sensitive information
  • Still need informal rules (e.g. type

rules)

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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Example of a grammar fragment (S-AST)

Key points

  • Extended BNF style
  • States allowed local class types

and component types

  • States allowed prefixes
  • Meta-variables, declarative

context-sensitive information

  • Verbose - intended for

specification, not implementation

Modelica specification about connectors: "No equations are allowed in the definition or in any of its components"

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Linköping University David Broman, davbr@ida.liu.se

Part I Why are specification improvements needed? Part II What to specify? Part III How to specify?

Concluding Summary

Thanks for listening!

Specification Goals

  • Unambiguous
  • Understandable
  • Expressive

What to specify

  • Transformation

aspects

  • Rejection aspects

How to specify

  • Current specification is

informal, e.g. open for interpretation

  • Evolutionary

"middle-way" approach

  • Specify INPUT and OUTPUT using grammars
  • Complements the informal semantics

Abstract Syntax Approach Next Step

  • Needs to be accepted

by Modelica Association as the fundamental approach.

  • Yet another

"specification" of a subset is less meaningful

  • There can only be one

specification...