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Model-Driven DevelopmentModel-Driven Development

Bran SelicIBM Distinguished Engineer

IBM Rational Software

Bran SelicIBM Distinguished Engineer

IBM Rational Software

22 IBM Software Group |

The $800M BombshellThe $800M Bombshell Deeply embedded in the software for controlling long-distance

phone traffic routing sat the following (kind of) code: …switch (caseIndex) {case‘A’: route = routeA;

…break;

…case‘M’: route = routeM;

…case‘N’: route = routeN;

…break;

…}

Deeply embedded in the software for controlling long-distance phone traffic routing sat the following (kind of) code: …switch (caseIndex) {case‘A’: route = routeA;

…break;

…case‘M’: route = routeM;

…case‘N’: route = routeN;

…break;

…}

Missing “break” Missing “break” statement!statement!

When this code ran (1990), the entire US Northeast lost long-distance phone service

When this code ran (1990), the entire US Northeast lost long-distance phone service


A Skeptic’s View of Software Models…A Skeptic’s View of Software Models…

“…bubbles and arrows, as opposed to programs, …never crash”“…bubbles and arrows, as opposed to programs, …never crash”

-- B. Meyer“UML: The Positive Spin”

American Programmer, 1997

-- B. Meyer“UML: The Positive Spin”

American Programmer, 1997

MonitorPH

MonitorPH

RaisePH

RaisePH

ControlPH

ControlPH

PH reached XPH reached X

enableenable

disabledisable

Current PHCurrent PH

startstart

stopstop

Input valvecontrol

Input valvecontrol


Models in Traditional EngineeringModels in Traditional Engineering As old as engineering (e.g., Vitruvius) Traditional means of reducing engineering risk

As old as engineering (e.g., Vitruvius) Traditional means of reducing engineering risk


Engineering ModelsEngineering Models Engineering model:

A reduced representation of some system that highlights the properties of interest from a given viewpoint

Engineering model:A reduced representation of some system that highlights the properties of interest from a given viewpoint

Functional ModelFunctional ModelModeled systemModeled system

We don’t see everything at once We use a representation (notation) that is easily understood for

the purpose on hand

We don’t see everything at once We use a representation (notation) that is easily understood for

the purpose on hand


How Engineering Models are UsedHow Engineering Models are Used

1. To help us understand complex systems Useful for both requirements and designs

Minimize risk by detecting errors and omissions early in the design cycle (at low cost)

• Through analysis and experimentation• Investigate and compare alternative solutions

To communicate understanding• Stakeholders: Clients, users, implementers, testers, documenters, etc.

2. To drive implementation The model as a blueprint for construction

1. To help us understand complex systems Useful for both requirements and designs

Minimize risk by detecting errors and omissions early in the design cycle (at low cost)

• Through analysis and experimentation• Investigate and compare alternative solutions

To communicate understanding• Stakeholders: Clients, users, implementers, testers, documenters, etc.

2. To drive implementation The model as a blueprint for construction


Models versus SystemsModels versus Systems

Differences due to:

• Idiosyncrasies of actual construction materials

• Construction methods

• Scaling-up effects

• Skill sets/technologies

• Misunderstandings

Can lead to serious errors and discrepancies in the realization

Differences due to:

• Idiosyncrasies of actual construction materials

• Construction methods

• Scaling-up effects

• Skill sets/technologies

• Misunderstandings

Can lead to serious errors and discrepancies in the realization

.

...


Characteristics of Useful ModelsCharacteristics of Useful Models Abstract

Emphasize important aspects while removing irrelevant ones Understandable

Expressed in a form that is readily understood by observers Accurate

Faithfully represents the modeled system Predictive

Can be used to answer questions about the modeled system Inexpensive

Much cheaper to construct and study than the modeled system

Abstract Emphasize important aspects while removing irrelevant ones

Understandable Expressed in a form that is readily understood by observers

Accurate Faithfully represents the modeled system

Predictive Can be used to answer questions about the modeled system

Inexpensive Much cheaper to construct and study than the modeled system

To be useful, engineering models must satisfy all of these characteristics!To be useful, engineering models must satisfy all of these characteristics!


SC_MODULE(producer){sc_outmaster<int> out1;sc_in<bool> start; // kick-startvoid generate_data (){for(int i =0; i <10; i++) {out1 =i ; //to invoke slave;}}SC_CTOR(producer){SC_METHOD(generate_data);sensitive << start;}};SC_MODULE(consumer){sc_inslave<int> in1;int sum; // state variablevoid accumulate (){sum += in1;cout << “Sum = “ << sum << endl;}

SC_CTOR(consumer){SC_SLAVE(accumulate, in1);sum = 0; // initialize };SC_MODULE(top) // container{producer *A1;consumer *B1;sc_link_mp<int> link1;SC_CTOR(top){A1 = new producer(“A1”);A1.out1(link1);B1 = new consumer(“B1”);B1.in1(link1);}};

A Bit of Modern Software…A Bit of Modern Software…

Can you spot the Can you spot the architecture?architecture?


…and its UML Model…and its UML Model

«sc_ctor»«sc_ctor»consumerconsumer


«sc_ctor»«sc_ctor»producerproducer«sc_ctor»«sc_ctor»

producerproducerstart out1 in1

«sc_link_mp»

link1

Can you spot the Can you spot the architecture?architecture?


The Software and Its ModelThe Software and Its Model



«sc_ctor»«sc_ctor»producerproducer«sc_ctor»«sc_ctor»

producerproducerstart out1 in1

«sc_link_mp»

link1

SC_MODULE(producer){sc_outmaster<int> out1;sc_in<bool> start; // kick-startvoid generate_data (){for(int i =0; i <10; i++) {out1 =i ; //to invoke slave;}}SC_CTOR(producer){SC_METHOD(generate_data);sensitive << start;}};SC_MODULE(consumer){sc_inslave<int> in1;int sum; // state variablevoid accumulate (){sum += in1;cout << “Sum = “ << sum << endl;}

SC_CTOR(consumer){SC_SLAVE(accumulate, in1);sum = 0; // initialize };SC_MODULE(top) // container{producer *A1;consumer *B1;sc_link_mp<int> link1;SC_CTOR(top){A1 = new producer(“A1”);A1.out1(link1);B1 = new consumer(“B1”);B1.in1(link1);}};


refine

NotStarted

Started

start

producer

Model Evolution: RefinementModel Evolution: Refinement

Models can be refined continuously until the specification is complete

Models can be refined continuously until the specification is complete

«sc_method»producer

«sc_method»producer

start out1

NotStarted

Started

start

producer

St1 St2

void generate_data(){for (int i=0; i<10; i++) {out1 = i;}}

/generate_data( )


The Remarkable Thing About SoftwareThe Remarkable Thing About Software

Software has the rare property that it allows us to directly evolve models into full-fledged implementations without changing the engineering medium, tools, or methods!

Software has the rare property that it allows us to directly evolve models into full-fledged implementations without changing the engineering medium, tools, or methods!

This ensures perfect accuracy of software models; since the model and the system that it models are the same thingThe model evolves into the system it was modeling

This ensures perfect accuracy of software models; since the model and the system that it models are the same thingThe model evolves into the system it was modeling


Model-Driven Style of Development (MDD)Model-Driven Style of Development (MDD)

An approach to software development in which the focus and primary artifacts of development are models (as opposed to programs)

Based on two time-proven methods

An approach to software development in which the focus and primary artifacts of development are models (as opposed to programs)

Based on two time-proven methods

SC_MODULE(producer)

{sc_inslave<int> in1;

int sum; //

void accumulate (){

sum += in1;

cout << “Sum = “ << sum << endl;}

«sc_module»«sc_module»producerproducer

start out1

(1) ABSTRACTION (2) AUTOMATION


start out1

SC_MODULE(producer)

{sc_inslave<int> in1;

int sum; //

void accumulate (){

sum += in1;

cout << “Sum = “ << sum << endl;}

Realm of modelinglanguages

Realm of tools


OMG’s Model-Driven Architecture (MDA)OMG’s Model-Driven Architecture (MDA) An OMG initiative

A framework for a set of open standards in support of MDD

An OMG initiative A framework for a set of open standards in support of MDD

MDA

OpenOpenStandardsStandards


start out1

(1) ABSTRACTION (2) AUTOMATION


start out1

Standards for:Standards for:

•Modeling languagesModeling languages

•Model transformationsModel transformations

•Software processesSoftware processes

•Model interchange…Model interchange…


ABSTRACTION: The Modeling Language ABSTRACTION: The Modeling Language DomainDomain


Modeling versus Programming LanguagesModeling versus Programming Languages Cover different ranges of abstraction Cover different ranges of abstraction

Level of Level of AbstractionAbstraction

high

low

ProgrammingLanguages

(C/C++, Java, …)

ModelingModelingLanguagesLanguages

(UML,…)(UML,…)


(UML,…)(UML,…)

LOdata layout, arithmeticaland logicaloperators,etc.

HIstatecharts,interactiondiagrams,architecturalstructure, etc.


(Any) ActionLanguage

Covering the Full Range of DetailCovering the Full Range of Detail

Level of Level of AbstractionAbstraction

high

low

ProgrammingLanguages

(C/C++, Java, …)


(UML,…)(UML,…)


(UML,…)(UML,…)

implementation level detail(applicationspecific)

Fine-grainlogic,arithmeticformulae,etc.

Fine-grainlogic,arithmeticformulae,etc.


Example: Combination of LanguagesExample: Combination of Languages

Combination of languages and representations Each optimized for its purpose

Combination of languages and representations Each optimized for its purpose

NotStarted

Started

start

producer

St1 St2


/generate_data( )


MDD Modeling Language RequirementsMDD Modeling Language Requirements

High expressive power Concepts closer to domain and distant from the

implementation technology “platform independent” concepts

Different domains need different concepts need domain-specific languages

Adequate semantic precision and clarity Models must be as accurate as their intended purpose

requires i.e., from “sketching” through code generation

High expressive power Concepts closer to domain and distant from the

implementation technology “platform independent” concepts

Different domains need different concepts need domain-specific languages

Adequate semantic precision and clarity Models must be as accurate as their intended purpose

requires i.e., from “sketching” through code generation


Domain-Specific LanguagesDomain-Specific Languages Where do we start? DSLs from “scratch”

Pro: - Highly optimized set of concepts

Con: - Need to reinvent many wheels (e.g., objects, interactions…)- Need to learn a new language for every domain- Need to provide full tool support for every domain

Example: SDL: a DSL for describing telecom protocols (refined since

1970) Latest version: UML profile (Z.109)

Where do we start? DSLs from “scratch”

Pro: - Highly optimized set of concepts

Con: - Need to reinvent many wheels (e.g., objects, interactions…)- Need to learn a new language for every domain- Need to provide full tool support for every domain

Example: SDL: a DSL for describing telecom protocols (refined since

1970) Latest version: UML profile (Z.109)


The Languages of MDAThe Languages of MDA Set of modeling languages for specific purposes Set of modeling languages for specific purposes

Meta ObjectMeta ObjectFacility (MOF)Facility (MOF)Meta ObjectMeta Object

Facility (MOF)Facility (MOF)

A modeling language for defining modeling languages

A modeling language for defining modeling languages

GeneralGeneralStandard UMLStandard UML

GeneralGeneralStandard UMLStandard UML

Common Common Warehouse Warehouse

Metamodel (CWM)Metamodel (CWM)

Common Common Warehouse Warehouse

Metamodel (CWM)Metamodel (CWM)

etc.etc.etc.etc.

For general OO modelingFor general OO modeling

For exchanging information about businessdata

For exchanging information about businessdata

Real-TimeReal-Timeprofileprofile

Real-TimeReal-Timeprofileprofile

EAI profileEAI profileEAI profileEAI profile

SoftwareSoftwareprocess profileprocess profile

SoftwareSoftwareprocess profileprocess profile

etc.etc.etc.etc.


AUTOMATION: The Tools DomainAUTOMATION: The Tools Domain


Primary Forms of Automation for MDDPrimary Forms of Automation for MDD

Model transformations Code generation, for analysis, for selective viewing,…

Computer-based validation Formal methods (qualitative and quantitative)

Computer-based testing Automated test generation, setup, and execution

Computer-based model execution Particularly execution of abstract and incomplete models

-- when most of the important decisions are made

Model transformations Code generation, for analysis, for selective viewing,…

Computer-based validation Formal methods (qualitative and quantitative)

Computer-based testing Automated test generation, setup, and execution

Computer-based model execution Particularly execution of abstract and incomplete models

-- when most of the important decisions are made


NotStarted

Started

start

producer

St1 St2


/generate_data( )

«sc_ctor»producer«sc_ctor»producer

start out1

main () {

BitVector typeFlags (maxBits);

char buf [1024];

cout << msg;

while (cin >> buf) {

for (int i = 0;i<maxBits;i++)

if (strcmp(typeTbl[i],buf)==0)

{typeFlags += i;

break;}

if ...

program (e.g., C++)

What is Automatic Code Generation?What is Automatic Code Generation? Automated translation into semantically equivalent programs Automated translation into semantically equivalent programs

Model transformer


Model ExecutionModel Execution

cos

cos

?? By formal analysis mathematical methods reliable (theoretically) software is very difficult to

model mathematically!

By formal analysis mathematical methods reliable (theoretically) software is very difficult to

model mathematically! ??

cos

cos

By experimentation (execution) more reliable than inspection direct experience/insight

By experimentation (execution) more reliable than inspection direct experience/insight

cos

cos

?? By inspection

mental execution unreliable


Automatic Code Gen: State of the ArtAutomatic Code Gen: State of the Art Efficiency

performance and memory utilization:within ±5-15% of equivalent manually coded system

Scalability compilation time (system and incremental change):

within 5-20% of manual process system size:

• Complete systems in the order of 4MLOC have been constructed using full code generation

• Teams of over 400 developers working on a common model

Efficiency performance and memory utilization:

within ±5-15% of equivalent manually coded system Scalability

compilation time (system and incremental change):within 5-20% of manual process

system size:• Complete systems in the order of 4MLOC have been constructed using full code

generation• Teams of over 400 developers working on a common model


Automating Engineering AnalysisAutomating Engineering Analysis

Inter-working of specialized tools via shared standards Inter-working of specialized tools via shared standards

Model EditingModel EditingToolTool

55

3.13.1

44

Model AnalysisModel AnalysisToolTool

AutomaticallyAutomaticallyderived analysisderived analysis

modelmodel

AutomaticallyAutomaticallyderived analysisderived analysis

modelmodel

Inverse automatedInverse automatedmodel conversionmodel conversionInverse automatedInverse automatedmodel conversionmodel conversion

2.52.5

QoS Annotations QoS Annotations OverlayOverlay

QoS Annotations QoS Annotations OverlayOverlay


Example: Schedulability AnnotationsExample: Schedulability Annotations

Sensors:SensorInterface

TelemetryGatherer:DataGatherer

«SAResource»

SensorData:RawDataStorage

TelemetryDisplayer: DataDisplayer

TelemetryProcessor:DataProcessor

Display:DisplayInterface

TGClock : Clock

TGClock : Clock

A.1:gatherData ( )

C.1:displayData ( )

B.1:filterData ( )

TGClock : Clock

A.1.1:main ( )

A.1.1.1: writeStorage ( )

B.1.1 : main ( )

B.1.1.1: readStorage ( )C.1.1.1: readStorage ( )

C.1.1 : main ( )

«SASituation»

{SACapacity=1,

SAAccessControl=PriorityInheritance}

«SASchedulable»

«SASchedulable» «SASchedulable»

«SATrigger»{SASchedulable=$R1,

RTat=('periodic',100,'ms')}«SAResponse»

{SAAbsDeadline=(100,'ms')}

«SAAction»{SAPriority=2,SAWorstCase=(93,'ms'),RTduration=(33.5,'ms')}

«SAAction»{RTstart=(16.5,'ms'),RTend=(33.5,'ms')}







«SAResponse»{SAPriority=3,SAWorstCase=(177,'ms'),RTduration=(46.5,'ms')}

«SAAction»{RTstart=(10,'ms'),RTend=(31.5,'ms')}

«SAAction»{RTstart=(3,'ms'),RTend=(5,'ms')}

«SAResponse»{SAPriority=1,SAWorstCase=(50.5,'ms'),RTduration=(12.5,'ms')}

ResultResult


Example: Deployment SpecificationExample: Deployment Specification

«SAEngine»{SARate=1,

SASchedulingPolicy=FixedPriority}

:Ix86Processor

«SASchedulable»


«SASchedulable»


«SASchedulable»


«SAResource»


«SAOwns»

«GRMdeploys»


Sensors:SensorInterface


«SAResource»




Display:DisplayInterface

TGClock : Clock

TGClock : Clock

A.1:gatherData ( )

C.1:displayData ( )

B.1:filterData ( )

TGClock : Clock

A.1.1:main ( )

A.1.1.1: writeStorage ( )

B.1.1 : main ( )

B.1.1.1: readStorage ( )C.1.1.1: readStorage ( )

C.1.1 : main ( )

{SACapacity=1,

SAAccessControl=PriorityInheritance}

«SASchedulable»

«SASchedulable» «SASchedulable»

«SATrigger»



«SASituation»

«SAAction»{SAPriority=2,SAWorstCase=(93,'ms'),RTduration=(33.5,'ms')}

«SAAction»{RTstart=(16.5,'ms'),RTend=(33.5,'ms')}

«SATrigger»



«SATrigger»



«SAResponse»{SAPriority=3,SAWorstCase=(177,'ms'),RTduration=(46.5,'ms')}

«SAAction»{RTstart=(10,'ms'),RTend=(31.5,'ms')}

«SAAction»{RTstart=(3,'ms'),RTend=(5,'ms')}

«SAResponse»{SAPriority=1,SAWorstCase=(50.5,'ms'),RTduration=(12.5,'ms')}

Example: Analysis ResultsExample: Analysis Results

{SASchedulable=$true,

{SASchedulable=$true

{SASchedulable=$true


ConclusionConclusion

The problem: We cannot keep implementing our applications using the

programming technologies of the late Fifties’ The demands on functionality, reliability, dependability,

availability, security, and performance demanded of modern software.

We need to, can do, and have already done better! MDA:

Increased levels of abstraction Increased levels of automation Open standards

The problem: We cannot keep implementing our applications using the

programming technologies of the late Fifties’ The demands on functionality, reliability, dependability,

availability, security, and performance demanded of modern software.

We need to, can do, and have already done better! MDA:

Increased levels of abstraction Increased levels of automation Open standards


QUESTIONS?([email protected])

QUESTIONS?([email protected])

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