This document discusses executable modeling for Android applications using statecharts. It presents a toy "Energy Assistant" mobile app modeled as a statechart to demonstrate the approach. The statechart model is executed on Android using the PauWare execution engine and an architecture that interfaces with Android events and actions. Executable modeling shifts efforts from programming to modeling and allows updating an app by loading a new model while keeping action implementations unchanged. This facilitates rapid prototyping and updating of Android apps through modeling rather than traditional programming.

1. AAnnddrrooiidd EExxeeccuuttaabbllee MMooddeelliinngg::
BBeeyyoonndd AAnnddrrooiidd PPrrooggrraammmmiinngg
Olivier Le Goaër
olivier.legoaer@univ-pau.fr
MobiApps # Session 1: Smart Systems
Barcelona, 2014

2. AAggeennddaa
 Context of Work
 Moving Executable Models to Android
 A software architecture powered by PauWare
API
 Conclusion & perspectives
Olivier Le Goaer @ MobiApps 2014

3. CCoonntteexxtt ooff WWoorrkk

4. WWee eenntteerreedd tthhee mmooddeelliinngg eerraa
 The power of software modeling
 Mental effort that differs from that required for programming
 A higher level of abstraction provides a better reasoning support
 supposed to be more concise, more intelligible, more agile…
 Model-driven engineering field (MDE)
 Promotes the « model everywhere » vision
 Models are considered first-class citizen during the software life-cycle
 UML was just the tip of the iceberg; DSL are now at the forefront
Olivier Le Goaer @ MobiApps 2014

5. SSttaattiicc vveerrssuuss ddyynnaammiicc mmooddeellss
 Classical MDE use static model
 A model = a blueprint for a software viewpoint that one can refer
to do stuff
 Testing, code generation, requirements elicitation, proofs, …
 A recent MDE trend is about dynamic model
 Extension that aims to breathe life into models
 A dynamic model = an animated/actioned blueprint that plays a
leading role
 Simulation and validation, rapid prototyping, ...
 There is no code generation; The model is sufficient in itself.
Olivier Le Goaer @ MobiApps 2014

6. EExxeeccuuttaabbllee mmooddeellss
 An execution engine is required
 An interpreter manages each execution step of the model under
execution
 Specific to each kind of models (petri nets, statecharts, workflows,
activity diagrams…)
 Statechart is a prominent example of
executable model
 Describes the behavior of something in terms of states and
transitions
 Is a general-purpose modeling language
 User navigation, Control flow... and generally speaking any object's life-cycle
Olivier Le Goaer @ MobiApps 2014

7. EExxeeccuuttaabbllee ssttaatteecchhaarrttss ffoorr rreeaall......
From “Statecharts: A visual formalism for complex systems” by David HAREL
Olivier Le Goaer @ MobiApps 2014

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AAnnddrrooiidd

9. IIlllluussttrraattiioonn wwiitthh aa ttooyy mmoobbAApppp
 Create a tiny mobApp « Energy Assistant »
 An avatar gives (not too serious) advices to the end-user based
on both the battery level and the usage of his device
 Statechart formalism to the rescue
 This kind of mobApp can be easily modeled with a statechart
 States will reflect the battery level
 Events will be mapped to Android system events
 Actions will be short notifications to the end-user (can be much more complex of
course)
 Accessible even to non-specialists of Android platform
 Requires a basic knowledge of how any mobile device operates
 This allows us to imagine that a customer can entirely model its needs in that way
Olivier Le Goaer @ MobiApps 2014

10. SSttaatteecchhaarrtt mmooddeelliinngg gguuiiddeelliinnee
 The control flow rises up to the model level
 Much more easy to understand and to maintain that when buried
in code
 Hence be careful that no control flow resides into the action code
A
B
[isOk] e1 / foo()
Olivier Le Goaer @ MobiApps 2014
public void foo() {
//do something
if (!isOk) {
//do something else
}
}
Interferes
with the
model !

11. EEnneerrggyy AAssssiissttaanntt''ss bbeehhaavviioorr
Olivier Le Goaer @ MobiApps 2014
 4 states
 Including a composite
 2 pseudos-states
 2 initials
 0 final
 7 transitions
 No guards
 7 Android-related
events
 1 kind of action :
« alert »

12. AAnnddrrooiidd mmooddeelliinngg?? RReeaallllyy??
 Classical code =
programming effort
 "I am writing the code of my
Android app. My focus is at
the program-level."
 Complex,
unmaintainable code
 Nested if, switch
statements, ...
 Flag variables and
« global » variables to
record what happened
previously...
Olivier Le Goaer @ MobiApps 2014
 Model-oriented code
= modeling effort
 "I am writing the code that
describes a statechart
model of my Android app.
My focus is at the model-level."
 Clear separation of
concerns
 Statechart description
 Actions' implementation
 Let an engine executes
directly the model

13. A software AArrcchhiitteeccttuurree ppoowweerreedd bbyy
PPaauuWWaarree AAPPII

14. PPaauuWWaarree EExxeeccuuttiioonn EEnnggiinnee
 PauWare engine (www.pauware.com)
 Lightweight execution engine for statechart models
 Implements the complete UML2 execution semantics specification
 API written in Java (hence ported effortlessly to Android)
Engine that executes the model
loaded (« run-to-completion »)
Olivier Le Goaer @ MobiApps 2014
JJaavvaa
PPaauuWWaarree AAPPII
Code/xml that describes the
statechart model to be loaded
Consumes an
event for each
execution step
Free implementation of
the actions
(called by reflection from the engine)

15. AArrcchhiitteeccttuurree oovveerrvviieeww
Java or xmi or scxml
Olivier Le Goaer @ MobiApps 2014
SERVICE
BROADCAST
RECEIVER
AAnnddrrooiidd OOSS
ANDROID
CONNECTOR
e1/foo
e1
public void foo() {
//do something
}
public void bar() {
//do other thing
}
A statechart model
runs-to-completion
PauWare
Execution
Engine
starts invokes

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Olivier Le Goaer @ MobiApps 2014
Active state
Triggered
transition

17. EEnneerrggyy AAssssiissttaanntt''ss AArrcchhiitteeccttuurree
Olivier Le Goaer @ MobiApps 2014
SERVICE
BROADCAST
RECEIVER
AAnnddrrooiidd OOSS
ANDROID
CONNECTOR
PauWare
Execution
Engine
ACTION_POWER_CONNECTED
void alert(String msg) {
Notification noti
= new Notification.Builder
...
}
runs-to-completion
starts invokes

18. SSccrreeeennsshhoottss
Assistant available
from the Launcher
Olivier Le Goaer @ MobiApps 2014
Assistant notification
POWER_CONNECTED

19. CCoonncclluussiioonn
 Executable models
 There is no code generation, the model is directly executed on a
target platform through an engine (.i.e. an interpreter)
 Android modeling rather than android
programming
 Shift the efforts on modeling activities (for those who are not
allergic to modeling ;-)
 Limited knowledge of the underlying platform is enough
 Stateshart formalism and beyond
 Widespread and well suited for aspects of apps (partly or entirely)
 A lot of further modeling languages can be useful...
Olivier Le Goaer @ MobiApps 2014

20. PPeerrssppeeccttiivvee:: uuppddaattee mmaaddee eeaassyy
 Ability to load a new model on-the-fly
 A model is just a (meta)data taken as input of the engine
 Actions' implementation have to stay unchanged
 Challenge: the execution continuum between old and new model
Fresh (meta)data retrieval
Olivier Le Goaer @ MobiApps 2014
SERVICE
BROADCAST
RECEIVER
AAnnddrrooiidd OOSS
ANDROID
CONNECTOR
runs-to-completion
PauWare
Execution
Engine
ACTION_POWER_CONNECTED
void alert(String msg) {
Notification noti
= new Notification.Builder
...
}
starts invokes
Model
Server
Google
Cloud
Messaging Push Notification

21. QQuueessttiioonnss??