software product-line engineering: a family-based software development process: introduction

Software Product-Line Engineering: A Family-

Based Software Development Process:

IntroductionDavid Weiss

[email protected]

2

Goals

• Bring the customer into the production loop for validation

• Separate the concerns of requirements determination and validation from design, coding, and testing

• Respond rapidly to changes in requirements

• Rapidly generate deliverable products– generate code and documentation– achieve high productivity (factor of 3-5 improvement)– achieve high quality (factor of 5 improvement)

• Be efficient– capture and leverage expertise– reuse systems

Session 1 10 May 2009 DMW

Session 1 10 May 2009 DMW 3

Engineer Application

Process Artifact

Key:

Validation & Acceptance

Customer(s)

Delivered Product

Requirements

Decisions

Components+Tools+Processes

Code & Documentation

4

Underlying Assumptions

• The Redevelopment Hypothesis: Most software development is mostly redevelopment.

• The Oracle Hypothesis: It is possible to predict the changes that are likely to be needed to a system over its lifetime.

• The Organizational Hypothesis: It is possible to organize both software and the organization that develops and maintains it in such a way as to take advantage of predicted changes.



Families

“We consider a set of programs to constitute a family whenever it is worthwhile to study programs from the set by first studying the common properties of the set and then determining the special properties of the individual family members.”

David L. Parnas

6

Airbus Beats Boeing in Huge Jetliner Deal with USAir (11/6/96)

• USAir, which had never bought a plane from Airbus, will purchase 120 Airbus A319s, A320s, and A321s...

• USAir’s current fleet is a hodgepodge of nine types of aircraft

• A simplified domestic fleet would allow USAir to lower costs.



Airbus: Unique Level of Commonality

• Conceived as a single aircraft programme, the A340 and A330 are virtually identical.

• They share the same fuselage, airframe, systems and cockpit technology as the original A300/A310.

• This commonality concept extends to the whole family of Airbus.


Importance of Commonality

• USAir will reduce costs by using one aircraft type• Airbus is reducing its production costs by reusing one

aircraft type


Examples of Families

• Airbus airplanes• IBM 360 computers• Internet browsers• Versions of 5ESSTM Switch Maintenance Software

– Software that enables changes in switch configuration while the switch is operating


Economics Of Families

CurrentPractice

Number of Family Members

Cumulative Cost

Product LineEngineering

{Initial Investment


Economics Of Families

CurrentPractice


Cumulative Cost

Product LineEngineering

{Initial Investment

1 2 3 4 5 6


1 2 3


4

Cumulative Savings

-I

S = N*(CT - CF) - I

Payback Point

SF - I

2*SF - I

3*SF - I

4*SF - I

5*SF - I

S = Cumulative savings

CT = Cost per family member with current practice

CF = Cost per family member with domain engineering

N = Number of family members

I = Investment in domain engineering for the family


Product Line

• A family of products designed to take advantage of its common aspects and predicted variabilities

• A product line may be decomposed into sub-families– Each subfamily contributes a member to members of the

product line– Sub-families may themselves be product-lines


FAST Process

• A process for defining families and developing environments for generating family members– Find abstractions common to the family– Define a process for producing family members– Design a language for specifying family members– Generate software from specifications

• Family-oriented Abstraction, Specification, Translation


Product Engineering Environment

A FAST Process

Domain Engineering

Product Engineering

Products

Feedback

Investment

Payback



Process Artifact

Key:

Validation & Acceptance

Customer(s)

Delivered System

Requirements

Decisions

Components+Tools+Processes

Code & Documentation

Product Engineering

Product EngineeringEnvironment

Products


Measuring The Effect In Legacy Systems That Have Been

Reengineered• Environment: Large legacy systems with many

domains• Goal: Measure effort and time per change before and

after a domain is reengineered• Data Needed

– Change history• Type, Time, Effort, Developers• Tags in the code that indicate reengineering

• Lucent results– Effort (or time) improvement of about a factor of 3


Interval Reduction

AB

CD

0

20

40

60

80

100

Percent PreviousInterval

ReducedInterval


FAST Applied To Switch Maintenance:

Product EngineeringFor SM Configuration Control


Switch Maintenance Configuration Control

• Software That Enables Changes In Switch Configuration While The Switch Is Operating– Ensures that requested configurations are valid and safe– Reconfigures– Example: Remove a Protocol Handler (PH) from service and

replace it with a spare

• New Switching Technology Requires New Configuration Controllers– New unit types


5ESS™ Switch Configuration

Lucent Technologies 5ESS


Product Engineering Environment For Configuration Control

• Language for specifying relationships among units• Relationship Architecture Designer (RAD)• Translator for RAD

– Generates C from RAD diagrams


Packet Service Unit Relationships


Packet Service Unit Relationships With Attributes

Relationship Architecture Design (RAD)


Domain Engineering

Product Engineering Environment

Domain Analysis

Domain Model

Domain Implementation

Analysis Document,Application Modeling

Language

Tools, Process


The Domain Model

• Conceptual Framework– Family Definition

• Commonalities and Variabilities Among Family Members– Parameters of Variation

• Common Terminology for the Family• Decision Model

– Economic Analysis– Product Line Architecture– Optional: Application Modeling Language (AML): Language for

stating requirements

• Mechanism for generating products– Composer or Compiler (AML)


The Conceptual Framework (1)• Qualify The Domain

– Is it economically viable?– Artifact: Economic Model

• Define The Family– What do members of the family have in common and how do

they vary?– Artifact: The Commonality/Variability Analysis

• Define The Decision Model– What decisions must be made to identify a family member?– Artifact: The Decision Model Table


The Conceptual Framework (2)• Create The Architecture

– What is a good modular structure and a good uses structure?

– Artifacts: Module Guide, Interface Specifications, Uses Relation

• Design The System Composition Mapping– What modules are needed for which decisions?– Artifacts: System Composition Mapping, Uses Relation

• Design The Product Engineering Environment– What are good mechanisms for using the decision model to

produce products or to generate products from the AML?– Artifacts: Decision Model GUI, Generator or Compiler (AML)


Product Engineering Environment For Configuration Control

ControlCode

ApplicationEnvironment

RAD Diagram

Translator

DataStructures

Configuration Controller

Functions

Rules And Operations

Translator


Family Artifact

Environment

Economic Model

Commonality Analysis

Decision Model

Family Design

Composition Mapping

Application Modeling Language

Application Engineering Process

Domain Model

Domain Implementation

Library

Generation Tools

Analysis Tools

Documentation

Application

Application Model

Application Documentation

Application Code

Tool Set Design

FAST ARTIFACTS


FAST

Qualify Domain

Engineer Domain


Model Application

Produce Application

Delivery and Operation Support

Manage Project

Change Family

Analyze Domain

Implement Domain

Define Decision Model

Analyze Commonality

Design Domain

Design Application Modeling Language

Create Standard Application Engineering Process

Design Application Engineering Environment

Implement Application Engineering Environment

Document Application Engineering Environment

FAST ACTIVITIES


Project Manager

Domain Manager

Environment Engineer

Domain Engineer

Application Manager

Application Producer

Application Engineer

System Maintainer/Supporter

FAST ROLES

Quantifying Benefits: Who’s Your Audience?

1) New Product effort decreases

Number of ProductsCum

ulat

ive

Effo

r t

Product LineDevelopment

TraditionalDevelopment

2) Time to Market decreases

3) Time for Customer Issues decreases

4&5) Feature development cost and time decreases

6) Time to integrate COTS decreases

7) Time to Qualify Products decreases

Number of ProductsTim

e to

Mar

k et


e to

clo

se is

s ues

Cost and TimeNum

ber

o f F

e atu

res


e to

Inte

g rat

e

Number of Products

Tim

e to

Qua

l ity



Summary

• Product lines take advantage of commonalities to make software development more efficient

• Reorganizing software production to take advantage of the family viewpoint is the key to improvement

• Generation of code and documentation from a model is the goal

Terminology

• Family• Product Line• Conceptual Model• Domain Engineering• Domain Model• Product Engineering (aka Application Engineering)• Product Engineering Environment• Decision Model• Commonality/Variability Analysis• System Composition Mapping• Application Modeling Language


Exercise 1: Scoping A FamilyPart 1

• Identify and name a family and describe 3 members of your family

Family:

Members:

1.

2.

3.


Exercise 1: Scoping A Family Part 2

Postulate an economic model for your family and define its key parametersAssumptions (For example, size of market, most valuable variabilities)

Parameters (For example, no.of family members, cost to produce a family member, time to break-even, profit as a function of members sold):


Exercise 1: Scoping A Family Part 2 (cont.)

Form of the model (equations, graph)


Teams

Role Responsibility Person

Systems Engineer Commonality/variability analysis, decision model

Architect Module, uses, process structures, interface specifications

Developer Module implementation

Tester & Integrator Module tests, System generation and verification

Project Manager Economic model, project plan



“If I have seen farther than others it is because I have stood on the shoulders of giants.”

-- Isaac Newton


“Everything should be as simple as possible, but no simpler.”

-- Albert Einstein

Backups



Family MembersNeeded by Customer 1



Initial FamilyMember For

Initial FamilyMember ForCustomer 1

Customer 3

Key

Family Member

Customer 1

Customer 2

Customer 3

1.2.1

1.2.2

1.2.1.1

3.1.1.1

3.1.1.2

3.2.1.1

3.1.1.1.1

Initial FamilyMember ForCustomers 2

Common domain

1.1

2.1

3.1

1.2

2.1.1

2.1.2

3.1.1

3.2.1 3.2.1.1.1

2.0

3.0

1.0


Selecting Your Targets

• Active domains– Frequent changes– Significant resources required

• Revenue-producing domains• Independent domains

– Little dependency on others– Often, near to the hardware


ApplicationModel

Analyses

RequirementsApplicationEngineer

Requirements/Needs Code/Documentation

Application Engineering

“... program structure should be such as to anticipate its adaptations and modifications. Our program should not only reflect (by structure) our understanding of it, but it should also be clear from its structure what sort of adaptations can be catered for smoothly. Thank goodness the two requirements go hand in hand.”

Edsger W. Dijkstra

On Program Families


Commonality Analysis of Configuration Control

• Approximately 20 staff -weeks– Spread over 6 months

– 6-12 experts

• Produced a Commonality Analysis– Definitions

– Commonalities

– Variabilities

– Parameters of Variation

• Reviewed by entire organization


Definitions

• Configuration: A set of units, the relationships between those units, and the status of the units.

• Primary condition: The availability of a unit: working, ready, unready, or unusable

• Realization: A sequence of steps from an initial configuration to a final configuration


Commonalities

C8. Every unit has a status.

C9. Every unit has a name and number, e.g., QLPS-0-1. Units with the same name provide

the same functionality.

C10. All units of the same name have the same set of conditions.


Variabilities

V5. Some unit names have inhibit states.

V7. The units to which a unit is related vary fromunit to unit.

V9. A child unit has one or more parent units. Theparent units may be of different names.

V10. The number of units of each parent unit name thatmust be working or ready...


Parameters of Variation

P5: inhibit state -- whether a unit name can have aninhibit state -- Boolean

P6: restore parallelism -- whether units of this namemay be restored in parallel

P22: parent name information -- by unit name

P25: parent units


Reusable Assets

• Validations -- generic algorithms for every unit type• Realizations -- generic algorithms for every unit type• Relationships

– data that is used to drive the generic algorithms– design information shared across development


Defining The Family: The Commonality Analysis

• Dictionary of terms

– Technical terms that define a vocabulary for the domain• Primary Condition: The availability of a unit: working:

ready, unready, or unusable• Commonalities: Assumptions that hold for every member of the

family

– Every unit must be in one of the four primary conditions.• Variabilities: Assumptions that define the range of variation for the

family

– Some unit names have inhibit states.• Parameters of Variation: Quantification of the variabilities

– Whether or not a unit name can have an inhibit state: Boolean


Maintenance Domain Structure

Human MachineInterface

Diagnostics

Hardware SoftwareInterface

MaintenanceAdministrator

Fault Detectionand Analysis

RoutineMaintenance

InitializationControl

ConfigurationControl

4


SMALL-D

Creating Configuration Controllers

SMALL-V SMALL-R

Domain Engineering

Application Engineering

VFSMC Data

Application

RAD

4

57

Advantages of FAST• Quick start-up

– Social process and documentation method are easy to learn– Other methods require special languages and tools

• Immediate benefits– Knowledge discovery and documentation has immediate impact– Other methods require investment in new process or tools before

any benefits

• Inclusive, not exclusive– All domain experts are welcome, they become owners – Other methods use specialists to record knowledge that is taken

from domain experts

• Incremental benefits for incremental investment

software product-line engineering: a family-based software development process: introduction

Documents

family of airbus

number of family membersi

individual family members

airbus a319s

advantage of predicted

sf i3

sf i4

sf i5