ser_ch3

8/12/2019 ser_ch3

http://slidepdf.com/reader/full/serch3 1/51

© 2005 IAS, Universität Stuttgart 1

SER

Processes and Process Models

3.1 Processes

3.2 Process Models

3.3 Real-Time Development Process

3.4 Workflows and Workflow Management

3.5 Standards and Process Tailoring

3.6 Software Process Improvement

3.7 Summary

Software Engineering for Real-Time Systems

8/12/2019 ser_ch3



SER

Objectives

– To introduce processes and process models

– To describe a number of different process models and when they

may be used

– To outline process models for specific software engineering activities

– To underline the importance of standards for software engineering

– To explain software process improvement.


8/12/2019 ser_ch3



SER

Processes

A process is a

Sequence of activities to reach a defined objective.

3.1 Processes

AB C

D E

persons(know-how,motivation,

management)

infrastructure,resources,

tools

methods

8/12/2019 ser_ch3



SER

– Coherent sets of activities for specifying, designing, implementing and

testing software systems

– A structured set of activities required to develop a software system

• Specification

•Design

• Validation

• Evolution

– A software process model is an abstract representation of a process.

It presents a description of a process from some particular perspective.

3.1 Processes

Software Processes

8/12/2019 ser_ch3



SER

Working with processes

3.1 Processes

process owner Processimprovement

metrics;

review results;project feedback

process

descriptionTechnology

change

trainingcoaching

User feedback

rolesWork products

check liststools

Development projectBusiness objectives

8/12/2019 ser_ch3



SER



3.1 Processes

3.2 Process Models

3.3 Real-Time Development process




3.7 Summary

8/12/2019 ser_ch3



SER

Process Models

In general:

Abstract representation of a (set of) process(es)

Description of a sequence of processes or activities,

that produce or process work products

3.2 Process Models

Software engineering:

A model (also plan or guideline),

which defines and aggregates processes,

methods, tools and roles

towards the development of a software system

IAS Process Model

8/12/2019 ser_ch3



SER

Archetypes

3.2 Process Models

1. Waterfall

Sequential towards one single result All others build upon this archetype!

2. Evolutionary

Builds upon results and creates iterationsV. 2V. 1

3. Incremental

Small steps towards final release.

8/12/2019 ser_ch3



SER3.2 Process Models

Waterfall model

possibility of overlapping stages

planning

definition

design

Implemen-

tation, test

Acceptance,delivery

8/12/2019 ser_ch3




Waterfall model problems

– Inflexible partitioning of the project into distinct sequential stages

– This makes it difficult to respond to changing customer requirements

– Therefore, this model is only appropriate when the requirements are

well-understood and frozen

– First tangible results only available with successful test. This makes project

management very difficult. Often delays and poor quality result from this

approach.

8/12/2019 ser_ch3



SER

Evolutionary development

– Process is represented as a spiral rather than as a sequence of activities

with backtracking

– Each loop in the spiral represents a phase in the process.

– No fixed phases such as specification or design - loops in the spiral are

chosen depending on what is required

– Risks are explicitly assessed and resolved throughout the process

3.2 Process Models

8/12/2019 ser_ch3



SER

Example: Spiral model of the software process

3.2 Process Models

PROGRESS

THROUGH

STEPS

CUMULATIVE

COST

EVALUATE ALTERNATIVES,

IDENTIFY, RESOLVE RISKSDETERMINE OBJECTIVES,

ALTERNATIVES,

CONSTRAINTS

DEVELOP, VERIFY

NEXT-LEVEL PRODUCT

PLAN NEXT PHASES

INTEGRATION

AND TEST

DEVELOP-

MENTPLAN

ROTS PLANLIFE CYCLE

PLAN

CONCEPT

OF OPERA-TION

SOFTWARE

ROTS

REQUIREMENTS

VALIDATION

DESIGN, VALIDATIONNAND VERIFICA-

TION

SOFTWARE

PRODUCT

DESIGN

RISK ANAYSIS

RISK ANAYSIS

RISK ANAYSIS

R

A PROTO-

TYPE1

PROTO-

TYPE2

PROTO-

TYPE 3

OPERATIONAL

PROTOTYPE

IMPLEMEN-TATION

ACCEPTANCETEST

INTEGRA-TION AND

TEST

UNIT

TESTCODE

DETAILEDDESIGN

1

COMMITMENT

PARTITION

8/12/2019 ser_ch3


8/12/2019 ser_ch3



SER

Evolutionary development problems

– Problems• Lack of process visibility

• Systems are often poorly structured

• Special skills (e.g. in languages for rapid prototyping) may

be required

• Unclear upfront resource estimation and allocation

– Applicability

• For small or medium-size interactive systems

• For parts of large systems (e.g. the user interface)

• For short-lifetime systems

3.2 Process Models

8/12/2019 ser_ch3



SER

Application of evolutionary approach:

Reuse-oriented development

– Based on systematic reuse where systems are integrated from existing

components or COTS (Commercial-off-the-shelf) systems

– Process stages

• Component analysis

• Requirements modification• System design with reuse

• Development and integration

– This approach is becoming more important but still limited experience

with it

– Typically applied for OO systems (frameworks, libraries)

3.2 Process Models

8/12/2019 ser_ch3



SER

Reuse-oriented development

3.2 Process Models

look-upclasses

in library

extract

classesif available

engineerclasses

if unavailable

constructnth iteration

of system

put newclasses

in library

OO analysis

OO designOO programming

OO testing

identifycandidate

classes

Customer

Communication

Planning Risk

Analysis

CustomerEvaluation Engineering,Construction &

Release

8/12/2019 ser_ch3



SER

– Rather than deliver the system as a single delivery, the development and

delivery is broken down into increments with each increment delivering part

of the required functionality

– User requirements are prioritised and the highest priority requirements

are included in early increments – Once the development of an increment is started, the requirements are

frozen though requirements for later increments can continue to evolve

3.2 Process Models

Incremental development

8/12/2019 ser_ch3




Incremental development (1)

stage X

stage X-1

stage X+1

pro-

ducts

pro-

ductsstage

planning

realization

analytical

QA

8/12/2019 ser_ch3



SER

Incremental development (2)

3.2 Process Models

increment 1

delivery of

1st increment

delivery of

2nd increment

delivery of3rd increment

calendar time

analysis design code test

increment 2analysis design code test

increment 3 analysis design code test

Stable build, integration test, system test

8/12/2019 ser_ch3



SER

– Customer value can be delivered with each increment so system

functionality is available earlier

– Early increments act as a prototype to help elicit requirements for later

increments

– Lower risk of overall project failure

– The highest priority system services tend to receive the most testing

3.2 Process Models

Incremental development advantages

8/12/2019 ser_ch3



SER

Application of incremental development:

Extreme programming

– Development and delivery of very small increments of functionality

– Relies on constant code improvement, user involvement in the

development team and pair wise programming

3.2 Process Models

8/12/2019 ser_ch3




Comparing the 3 process archetypes

ModelProject size and

complexity

Knowledge

of requirements

Changes

of requirements

Sche-

dule

smallCom-

plex

huge &

long

well-

knownvague never

Some-

timesoften urgent

Waterfall + o - + - + - - -

Evolutionary o + + o + + + o -

Incremental o + + + - + + o +

8/12/2019 ser_ch3



SER

Process Models for Specific Activities

3.2 Process Models

Typically process models are further broken down (hierarchy) to provideinsight into specific processes with a functional view

– project management

– requirements engineering

– software design – testing

– quality assurance

– configuration management

– change management – software evolution

8/12/2019 ser_ch3



SER



3.1 Processes

3.2 Process Models





3.7 Summary

8/12/2019 ser_ch3



SER

RT systems design process (1)

– Identify the stimuli to be processed and the required responses to

these stimuli

– For each stimulus and response, identify the timing constraints

– Aggregate the stimulus and response processing into concurrent

processes. A process may be associated with each class of stimulusand response


8/12/2019 ser_ch3



SER

RT systems design process (2)

– Design algorithms to process each class of stimulus and response. These

must meet the given timing requirements

– Design a scheduling system which will ensure that processes are started in

time to meet their deadlines

– Integrate using a real-time executive or operating system


8/12/2019 ser_ch3



SER

Timing constraints

– May require extensive simulation and experiment to ensure that these are

met by the system

– May mean that certain design strategies such as object-oriented design

cannot be used because of the additional overhead involved

– May mean that low-level programming language features have to beused for performance reasons


8/12/2019 ser_ch3



SER

Hardware and software design


Partition

requirements

Softwarerequirements

Hardwarerequirements

Softwaredesign

Hardwaredesign

Establishsystemrequirements

8/12/2019 ser_ch3



SER



3.1 Processes

3.2 Process Models





3.7 Summary

8/12/2019 ser_ch3



SER

Workflows and Workflow Management

Workflows are sets or relates processes that are

combined to have an end-to-end perspective

Workflow Management is the effective and efficient

handling of processes with that end-to-end

perspective, instead of local optimisation.


8/12/2019 ser_ch3



SER3.4 Workflows and Workflow Management

Workflows Cross Process Boundaries

area of operations

development

quality

assurance

configurationmanagement

project

management

activities and resultsin area of operations

legend: activity

result of an activity

relation

8/12/2019 ser_ch3



SER

Workflows Facilitate Early Checks


from

activity condition

SWE 1 approved

SWE 1

-

-

-

-

approved

-

-

-

-

interface plan,

segment-interfaces

DP integration plan

DP design

DP requirements

system design

system requirements

productuntil

activity condition

- -

-

SWE 3

SWE 3, 5, 6,

SWE 9

SWE 5

-

submitted

submitted

submitted

under way

QA

CM

8/12/2019 ser_ch3



SER



3.1 Processes

3.2 Process Models





3.7 Summary

8/12/2019 ser_ch3



SER

Standards and Process Tailoring

– Standards are a necessary precondition for reuse and flexibleorganizations

– With standardized procedures the completeness of results can be

guaranteed best - even in crisis situations.

– Defined intermediary results facilitate early validation and verification.

– Standardized usage of design notations (e.g. UML) facilitates readability,

maintainability and code generation / round-trip engineering

– Standardized processes improve estimation and accounting of expenses.

– Standards allow distributed, global development. They help with

outsourcing as well as subcontracting.


8/12/2019 ser_ch3



SER

IAS Software Process Standard


PM

QA CM

PM

QA CM

SEtest documents

developmentdocuments

Component test

Project planning

Definition

Design

ImplementationIntegration

Project attendance Project conclusion

procedure manual

developmentenvironment

project plan

PlanningReview

DefinitionReview

DesignReview

ImplementationReview

AcceptanceReview

specification control,checking

Configuration Administration

Data Assurance,Rights

Administration

projectconclusion report

reports,scheduling

IAS

student work

components

specification

programs,documents

test documents,protocols

Database

DataBase

programs,documents,protocols,KID

project plan,protocols

QA-require.,protocols

specification

QA-require.

System test

Test planning

released documents

project data

project data

QA require.QA result

activities and information flow

8/12/2019 ser_ch3



SER

Tailoring means getting concrete


?!

8/12/2019 ser_ch3



SER

Tailoring Steps


Standard

selectionrecommendations resp.cancellation conditions

selection of necessary

activities / products

identification of other project

specific execution conditions

call for bidding tailoring (at the beginning of a project)

project manual

evaluation of the project specific execution conditions

Specific project plan

technical tailoring(during progression of the project)

project specific

adjustment

8/12/2019 ser_ch3



SER

Managing Process Diversity


Process Model

Project Factors

commercialprocess out of

the box

one tailoredprocess for

project

managedprocess

diversity

System Size small large

Legacy Impacts greenfield big legacy

Component Structure few, isolated,

standardized

many, complex

interactions

Project Organization small,

collocated

distributed,

virtual teams

...

8/12/2019 ser_ch3



SER

Tools Support: process portal of SCT, ProNet


8/12/2019 ser_ch3



SER

Tools Support: Rational Unified Process


8/12/2019 ser_ch3



SER



3.1 Processes

3.2 Process Models





3.7 Summary

8/12/2019 ser_ch3



SER

Software Process Improvement

Software process improvement means success:

– identifying business objectives related to SW development

– prioritising them

– assessing and analysing own status

– agreeing on dedicated actions to overcome weaknesses and build on

strengths towards achieving the business objectives

– implementing these actions like a regular project

– measuring improvement


8/12/2019 ser_ch3



SER

Software Process Maturity is ...


“The extent to which a specific process is

explicitly defined, managed, measured, and

effective. Maturity implies a potential for growth

in capability and indicates both the richness...and

consistency with which software processes are

applied across the organization.”

“The extent to which a specific process is

explicitly defined, managed, measured, and

effective. Maturity implies a potential for growth

in capability and indicates both the richness...and

consistency with which software processes are

applied across the organization.”

Capabi l i ty Matur i ty Model

8/12/2019 ser_ch3



SER

The Capability Maturity Model


Optimizing (5)Focus on processimprovement

Optimizing (5)Focus on process

improvement

Managed (4)Process measured

and controlled

Managed (4)Process measured

and controlled

Defined (3)Process characterized,fairly well understood

Defined (3)Process characterized,fairly well understood

Repeatable (2)Can repeat previously

mastered tasks

Repeatable (2)Can repeat previously

mastered tasks

Initial (1)Unpredictable &poorly controlled

Initial (1)Unpredictable &poorly controlled

ContinuousImprovement

ProcessMeasurement

ProcessDefinition

BasicManagement

control

INOU

INOUT

OUTIN

8/12/2019 ser_ch3



SER

Sustainable Change Means Focus on Business Objectives


EffectiveChanges

ActionPlanning

Assessment

Feedback Loop• Project performance• Customer Satisfaction• Metrics• Quality Checks• Root Cause Analysis

Process Improvement …• … evaluates results• … draws conclusions• … is focused on business

BusinessObjectives

8/12/2019 ser_ch3



SER

IDEAL: A Model to Improvement for Software Organizations


5 phases - 47 taskstowards CMM-based

tangible improvements

SetContext

BuildSponsor-ship

Charter Infra-structure

CharacterizeCurrent &DesiredStates

DevelopRecommen-

SetPriorities Develop

Approach

Plan Actions

CreateSolution

Pilot/TestSolution

RefineSolution

ImplementSolution

AnalyzeandValidate

ProposeFuture

Actions

Stimulus

forChange

Initiating

Diagnosing

Establishing

Acting

Learning

dations

8/12/2019 ser_ch3



SER

Yet another view


L5

From our perspective,level 1 organizations are

mostly running into walls,

level 2 and 3 organizations are

learning where the walls are,

and level 4 and 5 organizations are

building walls for the other guys

to run into.

John Major

prev. exec. VP Qualcom and Motorola

8/12/2019 ser_ch3



SER



3.1 Processes

3.2 Process Models


3.4 Workflows and Workflow Management3.5 Standards and Process Tailoring


3.7 Summary

8/12/2019 ser_ch3



SER3.7 Summary

Summary (1)

– Software processes are the activities involved in producing and evolving asoftware system. They are represented in a software process model

– General activities within all process models are requirements engineering,

design and implementation, validation and evolution

• Requirements engineering is the process of developing a software

specification

• Design and implementation processes transform the specification to

an executable program

• Validation involves checking that the system meets to its specification

and user needs• Evolution is concerned with modifying the system after it is in use

8/12/2019 ser_ch3



SER

Summary (2)

– Generic process models describe the organisation of software processes

– There are 3 archetypes of process models

• Waterfall

• Evolutionary

• Incremental

– Workflows are collections of related interacting processes.

– Standards facilitate reuse and cooperation.

– The Capability Maturity Model is a de-facto standard for successful

process improvement.

3.7 Summary

8/12/2019 ser_ch3



SER

Further Information

3.7 Summary

Successful Software ProcessImprovement

by Robert B. Grady$49.99Hardcover - 350 pages (May1997)Prentice HallISBN: 0136266231

Extremely useful compilation onprocesses, process management

and process improvement.Practical insight into what HP didto improve their variety of SWprocesses.

ser_ch3

Documents