This document summarizes a presentation given by Olivier Le Goaër on executable modeling and dynamic adaptation. It provides a short biography of Le Goaër, discusses domain-specific languages and different shapes they can take, and how models are taking on a more dynamic role at runtime. It explores controversies around executable models and components of executable modeling built with model-driven engineering. Finally, it discusses approaches to executable modeling, model adaptation, and implementation choices for adaptive executable modeling.

1. Olivier Le Goaër
olivier.legoaer@univ-pau.fr
Séminaire LIRMM
Montpellier, 30/09/2016
Executable modelingExecutable modeling
&&
dynamic adaptationdynamic adaptation

2. 2/31
A short bioA short bio
 Positions
● Ph.D in 2009 – AeLoS team, LINA
● Associate Professor since 2010 – MOVIES team, LIUPPA
 Research topics
● Software Evolution/Adaptation
● Software Architecture
● Model-Driven Engineering
 Hobbies
● Mobile technologies
● Web technologies

3. 3/31
Domain-specific languages (DSL)Domain-specific languages (DSL)
 General Purpose Languages
● Not targeted to a particular kind of problem, but to any kinds of
software problem
 Domain-Specific Languages
● Targeted to a particular kind of problem
– with dedicated notations (textual or graphical), support (editor, checkers, etc.)
● Promises: more « efficient » languages for resolving a set of
specific problems in a domain
● Each concern described in its own language
– For software developpers (modeling, programming, querying, building,
documenting, ...), for software architects (ADL), for statisticians (R), for biologists, for
sociologists, ...

4. 4/31
Shapes for a DSLShapes for a DSL
 Internal
● Hosted by a
GPL
 External
● Stand-alone
 Implicit
● API-like
C# & Linq SQL Querydsl SQL
Java API
QCustomer customer;
customer = new QCustomer("c");
SQLQuery<?> query =
new SQLQuery<Void>(connection);
List<String> lastNames =
query.select(customer.lastName)
.from(customer)
.where(customer.firstName.eq("Bob"))
.fetch();
System.out.print(lastNames);
SELECT lastName
FROM customer
WHERE firstName = 'Bob';
var queryBobCustomers =
from cust in customer
where cust.firstName == "Bob"
select cust.lastName;
foreach (var n in queryBobCustomers)
{
Console.WriteLine(n);
}

5. 5/31
Shapes for a DSLShapes for a DSL
 Internal
● Hosted by a
GPL
 External
● Stand-alone
 Implicit
● API-like
C# & Linq SQL Querydsl SQL
Java API
QCustomer customer;
customer = new QCustomer("c");
SQLQuery<?> query =
new SQLQuery<Void>(connection);
List<String> lastNames =
query.select(customer.lastName)
.from(customer)
.where(customer.firstName.eq("Bob"))
.fetch();
System.out.print(lastNames);
SELECT lastName
FROM customer
WHERE firstName = 'Bob';
var queryBobCustomers =
from cust in customer
where cust.firstName == "Bob"
select cust.lastName;
foreach (var n in queryBobCustomers)
{
Console.WriteLine(n);
}

6. 6/31
Models are taking a new roleModels are taking a new role
« marauders map » – Harry Potter
Model playing a static role
(design-time)
Model playing a dynamic role
(run-time)
● Tells us about the
structure of the castle
(every classroom,
every hallway, and
every corner)
● Tells us about moving
persons (shows foot
prints)

7. 7/31
Crossing the demarcation lineCrossing the demarcation line
Model of a
system
(conforms to a
metamodel)
S
Running
system
IN
TER
PR
ETATIO
N
Running system
=
model under execution
Design-time
Run-time
C
O
M
PILATIO
N
</xml>
sub{ }
MDA ®
MM
exec(M)exec(M)

8. 8/31
Executable modeling (xModeling)Executable modeling (xModeling)
 Compilation
● Translational semantics
– Code generation in a target language
 Direct execution (~VM/interpreter)
● Operational semantics
– Using an « action » language
– Using a M2M transformation (rare in practice)
 Breathing life into models
● Simulation, V&V, rapid prototyping...
● Ultimately, skip the implementation stage !

9. 9/31
Controversies and debatesControversies and debates
 Executable models "can be run, tested,
debugged, and measured for performance"
 UML / fUML as prominent examples
● Is a class diagram executable? Alone ?
● Is a paquage diagram executable?
● Is a sequence diagram executable?
 Raises the question of an executable nature
● Behavior of a software system captured by a model M
● Ability to define a current execution state within M
● Ability to compute the next state (aka « step ») within M

10. 10/31
xModeling built with MDExModeling built with MDE
 Meta-models are just a specific OO data
structures to represent abstract syntax trees
● Operational semantics = computation steps and runtime data
● A VM/interpreter is a program working with such AST and that
implements a given operational semantics
 Executable metamodeling
● xMOF (eXecutable MOF)
● Kermeta
● Ecore + body of operation(s) written Java/EMF
● …

11. 11/31
xModeling's componentsxModeling's components
Abstract Syntax
Metamodel
+
Well-formedness rules
Concrete Syntax
Graphical or textual
Semantics
How it behaves at runtime ?

12. 12/31
Modeling with StatechartsModeling with Statecharts
--The instance of the finite state machine is unique (root)
context StateMachine inv singleStateMachine:
StateMachine.allInstances()->size() = 1 and self.container.oclIsUndefined()
--All the states are included in composites except the finite state machine herself
context State inv containerForAllStates:
not self.oclIsTypeOf(StateMachine) implies not self.container.oclIsUndefined()

13. 13/31
Train Cruise Control ModelTrain Cruise Control Model

14. 14/31
xModeling with StatechartsxModeling with Statecharts
runToCompletion()
isActive:boolean
0..1
lastKnownActiveState
-- When an history state exists and references a state, the latter must belongs to the composite
context CompositeState inv historyInComposite:
if self.historyState.oclIsUndefined()
then true
else
if self.historyState.referencedState.oclIsUndefined()
then true
else self.states->includes(self.historyState.lastKnownActiveState)
endif
endif

15. 15/31
xModeling with StatechartsxModeling with Statecharts
runToCompletion()
isActive:boolean
0..1
lastKnownActiveState
-- When an history state exists and references a state, the latter must belongs to the composite
context CompositeState inv R3:
if self.historyState.oclIsUndefined()
then true
else
if self.historyState.referencedState.oclIsUndefined()
then true
else self.states->includes(self.historyState.lastKnownActiveState)
endif
endif
//operationnal semantics of UML2
aspect class StateMachine {
operation runToCompletion(e : Event)
is do
// suivre la transition trouvée en activant l'état
// cible et en modifiant en conséquence la hiérarchie d'états actifs
end
}
//operationnal semantics of UML2
aspect class StateMachine {
operation runToCompletion(e : Event)
is do
// suivre la transition trouvée en activant l'état
// cible et en modifiant en conséquence la hiérarchie d'états actifs
end
}

16. 16/31
Running system = exec(Model)Running system = exec(Model)

17. 17/31
Model@run.timeModel@run.time
 Overloaded term
● Deals originally with software
adaptation issues at runtime
 Advantage
● Provides a reasoning support
on a running system
 Drawback
● Holding a causal link: M has to
remain the strict reflect of S
MM
SS
adaptation ?
représentation modification
Adaptation
loop

18. 18/31
Model@run.time + xModelingModel@run.time + xModeling
 Treats the specific case where the considered
running system is a model under execution
 Idea : collapsing the adaptation loop
● Solves the causal link issue...
● ...but the merge may leads to a burdened model M''
M
S = exec(M')S = exec(M')
adaptation ?
représentation modification S = exec(M'')
adaptation ?
modification
collapse

19. 19/31
Non-supervised adaptation (self-*)Non-supervised adaptation (self-*)
 Detect a situation requiring adaptation
● Known versus unknown context (e.g. a new signal)
– Green runtime event is sometimes ignored (designer's choice at design-time)
– White runtime event is actually unknown at design-time
 Perform adaptation actions
● CRUD operators on any runtime data
 Metamodel specialization unlocks adaptation
● Model (sub)typing : adding new metaclasses and new constraints
– Adding new operations accordingly : for (a) detect and (b) perform
● Choosing the right level of specialization is tactful
– Domain adaptations are rare but apply on any model instance of the metamodel
– Business adaptations are frequent but only apply on some models

20. 20/31
Subtyped Cruise Control ModelSubtyped Cruise Control Model
com
pleteness
tagged
value
+
Consistency

21. 21/31
Dynamic adaptation of the modelDynamic adaptation of the model

22. 22/31
Adaptable xModelingAdaptable xModeling
RunToCompletion()*
-- Each state must be associated to a transition for each identified event
context State def: knownEvents : Set(String) = Set{...};
context State inv Completeness:
self.knownEvents -> forAll( e | self.existsTransitionFor(e))
-- A transition tagged with {p, v} leads to a state also tagged with with {p, v}
context StateMachine inv Consistency:
...
...

23. 23/31
Adaptable xModelingAdaptable xModeling
RunToCompletion()*
-- Each state must be associated to a transition for each identified event
context State def: knownEvents : Set(String) = Set{...};
context State inv Completeness:
self.knownEvents -> forAll( e | self.existsTransitionFor(e))
-- A transition tagged with {p, v} leads to a state tagged with with {p, v}
context StateMachine inv Consistency:
...
...
//adaptation operational semantics
aspect class StateMachine {
operation runToCompletion(e : Event)
is do
if not e.isKnown() then
//introduces the new state and transitions thereof
end
//same as usual (nominal behavior)
end
}
//adaptation operational semantics
aspect class StateMachine {
operation runToCompletion(e : Event)
is do
if not e.isKnown() then
//introduces the new state and transitions thereof
end
//same as usual (nominal behavior)
end
}
aspect class Event {
operation isKnown() : Boolean
is do
//checks if an event is unknown or not
end
}
aspect class Event {
operation isKnown() : Boolean
is do
//checks if an event is unknown or not
end
}isKnown()*

24. 24/31
From craft to engineering with MDEFrom craft to engineering with MDE
Modeling
xModeling
Adaptable
xModeling
Metamodel (static)
+ [exec. translational semantics]
Metamodel (static + dynamic)
+ exec. operational semantics
Metamodel (static + dynamic + adaptative) +
adapt. operational semantics

25. 25/31
Adaptation extends executionAdaptation extends execution
 Execution semantics
● Deals with the nominal behavior (known context)
● Operation(s) only apply on the dynamic part (the static part is on
read-only mode)
 Adaptation semantics
● Is-a-kind-of execution semantics
● Deals with extra-ordinary situation (unknown context)
● Operation(s) may apply on all parts (static, dynamic, adaptation)
 The two kinds of semantics are mixed

26. 26/31
Implementation ChoicesImplementation Choices
 Classic programming
● Adaptation is tangled into execution
 OO programming
● Adaptation overrides execution (and calls « super »)
 Contract-based programming
● Adaptation occurs when a precondition of execution is violated
 Aspect-oriented programming
● Adaptation is woven into execution
 xModeling !
● Adaptation is modeled with a DSL and calls back to execution

27. 27/31
xModeling built without MDExModeling built without MDE
 PauWare engine (www.pauware.com)
● Execution engine (VM) for statechart models
● Implements the complete UML2 execution semantics specification
● API written in Java (hence ported effortlessly to Android)
JavaJava
PauWare APIPauWare API
Code/xml that describes the
statechart model to be loaded
Engine that executes the model
loaded (« run-to-completion »)
Free implementation of
the actions
(called by reflection from the engine)
Consumes an
event for each
execution step

28. 28/31
Android + PauWareAndroid + PauWare
SERVICE
BROADCAST
RECEIVER
Android OS
ANDROID
CONNECTOR
e1/foo
e1
public void foo() {
//do something
}
public void bar() {
//do other thing
}
A statechart model
runs-to-completion
starts invokes
PauWare
Execution
Engine
Java
xmi
scxml

29. 29/31
Supervised adaptationSupervised adaptation
 Ability to load a new model on-the-fly
● A model is just a runtime data taken as input of the engine
● Actions' implementation have to stay unchanged
SERVICE
BROADCAST
RECEIVER
Android OS
ANDROID
CONNECTOR
events
runs-to-completion
starts invokes
PauWare
Execution
Engine
Model
Server
Google
Cloud
Messaging
Push
Notification
Fresh data retrieval
Adapter
e1/foo
public void foo() {
//do something
}
public void bar() {
//do other thing
}

30. 30/31
World Wide Modeling (wwm)World Wide Modeling (wwm)
 MDE-specific URI
● model://host[:port]/M3/M2/M1
– model://localhost/Ecore/UML2/train
– model://localhost/Ecore/OCL/
 Commands
● model://host/M3?list
● model://host/M3/M2?info
● model://host/M3/M2/M1#fragment
 Getting started (requires )
● $> npm install wwm
● JavaScript API for client-side and server-side programming

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Thank you for your attentionThank you for your attention
?