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 Linköping University David Broman, davbr@ida.liu.se
2 Outline of the Talk Part I - Why are specification improvements needed? Specification Goals and Problems Part II - What to specify? Part III - How to specify? Previous Different Rejection Transformation Attempts Approaches Aspect Aspect Abstract Syntax Approach Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
3 Part I Why are specification improvements needed? Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
4 Problem: Interpreting the specification Interpretation of syntax and semantics Simulation Tool Modelica Language Specification � Dymola � Modelica System Designer Problem � MOSILAB - The Modelica Specification is open for interpretation � SimulationX - May result in incorrect and incompatible tools � OpenModelica Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
5 Specification goals Unambigious "Can only be interpreted in exactly one way" Understandable "Easy to grasp with moderate computer science knowledge" Expressive "State the syntax and semantics in a compact manner" Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
6 An evolutionary "middle-way" strategy Revolutionary Strategy Very large specification. Evolutionary Strategy . Abstract Syntax Approach Formal approach Informal approach e.g. operational semantics e.g. natural language text Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
7 Part II What to specify? Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
8 What should be specified? Syntax Semantics - the structure - the meaning R L sineVoltage R=10 L=1 Inertia1 k=1 spring E... c=1 J=0.1 1. Transformation Aspect G world y revolute r={L1,0,0} r={L2,0,0} a b b a b a b a bodyBox bodyBox1 n={0,0,1} n={0,0,1} x actuatedRev... Modelica Model Simulation Result R L sineVoltage R=10 L=1 Inertia1 k=1 spring E... c=1 2. Rejection Aspect J=0.1 G world y revolute r={L1,0,0} r={L2,0,0} a b b a b a b a bodyBox bodyBox1 n={0,0,1} n={0,0,1} x actuatedRev... Modelica Model Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
9 Transformation Aspect What is actually the result of an execution? R L sineVoltage R=10 L=1 Inertia1 k=1 spring E... c=1 J=0.1 G world y revolute r={L1,0,0} r={L2,0,0} a b b a b a b a bodyBox bodyBox1 n={0,0,1} n={0,0,1} x actuatedRev... Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
10 Rejection Aspect What is actually a valid Modelica model? R L R=10 L=1 sineVoltage Inertia1 k=1 spring E ... c=1 J=0.1 G world y revolute r={L1,0,0} r={L2,0,0} a b b a b a b a bodyBox bodyBox1 n={0,0,1} n={0,0,1} x actuatedRev... Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
11 Part III How to specify? Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
12 Previous Specification Attempts Types in Modelica Instance Creation (Elaboration) (Broman, Fritzson & Furic, 2006) (Mauss, 2005) - Only transformation aspect - Clarify the type concept in Modelica - Subset of the language - Concerns only the rejection aspect RML and Natural Semantics Modelica Specification (Kågedal & Fritzson, 1998) (Modelica Association, 2005) - 1998, large subset of specfication - Informal semantics, natural language - hard to get an overview of - became very large - Concrete syntax - now the code base for OpenModelica Formal approach Informal approach Abstract Syntax e.g. operational semantics e.g. natural language text Approach Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
13 Abstract Syntax as a Middle-Way Strategy Elaboration (transformation and rejection aspects) � Input: Implicitly specified using concrete syntax Scanning, Parsing => � Output: Not specified � Abstract Syntax Tree (AST) Transformation: Informally specified using natural language Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
14 Transformation and Rejection Aspects Rejection Aspect Transformation Aspect � � More restrictive than the concrete Precise specification of input syntax grammar and output (grammar) � � Include context sensitive information Transformation still informal � Still need informal rules (e.g. type rules) Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
15 Example of a grammar fragment (S-AST) Modelica specification about connectors: "No equations are allowed in the definition or in any of its components" 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 Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
16 Concluding Summary How to specify What to specify Specification Goals � Current specification is � � Transformation Unambiguous informal, e.g. open for aspects � Understandable interpretation � Rejection aspects � Expressive � Evolutionary "middle-way" approach Abstract Syntax Approach Next Step � Specify INPUT and OUTPUT using grammars � Needs to be accepted � Complements the informal semantics by Modelica Association as the fundamental approach. � Yet another "specification" of a subset is less meaningful Thanks for listening! � There can only be one specification... Part I Part II Part III Why are specification What to specify? How to specify? Linköping University improvements needed? David Broman, davbr@ida.liu.se
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