Towards Constraint-Based Model Types: A Generalised Formal Foundation for Model Genericity

Towards Constraint-Based Model Types: A Generalised

Formal Foundation for Model Genericity

Steffen Zschaler

22 July 2014

VAO, York

Towards Constraint-Based Model Types: A Generalised

Formal Foundation for Model Genericity

Steffen Zschaler

22 July 2014

VAO, York

Reuse in model management

22/07/2014 2

Model transformation specifications

Untyped

• No documentation

of assumptions

• No checking of

applicability for a

given model

Typed over one

specific meta-model

• Only work for models

that instantiate the

particular meta-model

• Need to rewrite

transformation from

scratch for any

similar meta-model.

Reuse in model management

22/07/2014 2

Model transformation specifications

Untyped

• No documentation

of assumptions

• No checking of

applicability for a

given model

Typed over one

specific meta-model

• Only work for models

that instantiate the

particular meta-model

• Need to rewrite

transformation from

scratch for any

similar meta-model.

We need a type system that is both sufficiently lax and

sufficiently precise to capture the best of both worlds.

(NB Can think of such model types as views on the

models to be manipulated.)

Existing approaches

• Two attempts at such type systems

exist:

– Model Typing (Steel, Guy, Combemale, et al.)

– Model Concepts (de Lara, Guerra, Rose, et

al.)

• All have problems

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Example problems

22/07/2014 4

mmo NewSM (s : Simple) {

s += new StateMachine ()

}

Example problems

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mmo NewSM (s : Simple) {

s += new StateMachine ()

}

StateMachineState

name: String

Transition

event: String

initialState

0..1

containedState *

src

1

tgt

1

incoming

*

*

outgoing

Difference between Simple and Mandatory-startMandatory-start <:Steel Simple

Example problems

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mmo NewSM (s : Simple) {

s += new StateMachine ()

}

StateMachineState

name: String

Transition

event: String

initialState

0..1

containedState *

src

1

tgt

1

incoming

*

*

outgoing

Difference between Simple and Mandatory-start

Error: Allows passing in

Mandatory-start instance, but breaks it.

Mandatory-start <:Steel Simple

mmo NewSM (s : Mandatory-start) {

sm := new StateMachine () ;

sm.initialState += new State () ;

s += sm

}

Example problems

22/07/2014 4

StateMachineState

name: String

Transition

event: String

initialState

0..1

containedState *

src

1

tgt

1

incoming

*

*

outgoing

Difference between Simple and Mandatory-startMandatory-start <:Guy Simple

mmo NewSM (s : Mandatory-start) {

sm := new StateMachine () ;

sm.initialState += new State () ;

s += sm

}

Example problems

22/07/2014 4

StateMachineState

name: String

Transition

event: String

initialState

0..1

containedState *

src

1

tgt

1

incoming

*

*

outgoing

Difference between Simple and Mandatory-start

Over-restriction: Would work with any

Simple instance, but cannot specify.

Mandatory-start <:Guy Simple

Two general problems

1. Focus on external contracts

– Can validate invocations but not

implementations

2. No formal definition

– Cannot analyse correctness

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Towards a solution

1. Provide a formalisation

– Explicit type system for model types

– Explicitly include constraints on the structure

of acceptable models

2. Define a notion of an internal contract

– In the paper defined through a set of type

inference rules

– Key really: Dataflow analysis of MMO

implementation

22/07/2014 6

Example

22/07/2014See paper for type rules

Example

22/07/2014See paper for type rules

Example

22/07/2014

Statements typed by

their effect on

system states

data flow analysis

States assign model types

to variables (see paper)

See paper for type rules

Example

22/07/2014See paper for type rules

Example

22/07/2014

Append rule generates

additional constraints.

Here: Forbids mandatory

associations from StateMachine.

See paper for type rules

Example

22/07/2014See paper for type rules

Example

22/07/2014See paper for type rules

Example

22/07/2014See paper for type rules

Example

22/07/2014See paper for type rules

Conclusions and Outlook

• Need better understanding of generic

model types

– Internal contracts

– Constraint-based model types may provide

the basis

• Proper formalisation needed

• Limits of data-flow analysis?

22/07/2014 8

QUESTIONS?

Steffen Zschaler

[email protected], @szschaler

22/07/2014 9