Software Engineering: A Practitioner’s Approach, 6/e
Chapter 2, 3, &4
Process
copyright © 1996, 2001, 2005
R.S. Pressman & Associates, Inc.
For University Use Only
May be reproduced ONLY for student use at the university level
when used in conjunction with Software Engineering: A Practitioner's Approach.
Any other reproduction or use is expressly prohibited.
1
Software Process
A framework for the tasks that
are required to build high-quality
software.
A process defines who is doing
what, when, and how to reach a
certain goal.
2
A Process Framework
Process framework
Framework activity #1
work tasks
work products
milestones & deliverables
QA checkpoints
…
Framework activity #n
…
Umbrella Activities
3
Generic Framework Activities



Communication: Communication and collaboration with the
stakeholders and encompasses requirement gathering and
other activities.
Planning: Establishment of a plan: the technical tasks, risks,
resources, work products, and a work schedule
Modeling:

Analysis of requirements: better understanding of requirements


Design: that achieves the requirements


Data design, architectural design, interface design, detailed design
Construction



Req. gathering, elaboration, negotiation, spec, and validation
Code generation: manual or automated
Testing: uncover errors.
Deployment: Delivery of software for customer evaluation
with feedback.
4
Communication: Requirements Gathering
Task set:
Simple Project
Complex Project
1.
2.
1.
2.
3.
4.
5.
6.
List stakeholders
Informal meeting with
stakeholders
Ask each to list of features
and functions
Determine the final list of
requirements
Prioritize requirements
Note areas of uncertainty
3.
4.
5.
6.
7.
8.
9.
10.
11.
List stakeholders
Meet stakeholders separately to determine
overall wants and needs
Build a preliminary list of functions and
features
Schedule and conduct a series of facilitated
requirements gathering meetings
Produce informal scenarios as part of each
meeting
Refine scenarios
Build revised requirements
Prioritize requirements
Package requirements for incremental
delivery
Note constraints and restrictions
Discuss methods for validating the system
5
Umbrella Activities

Software project management


Formal technical reviews


Defines criteria for reuse and establishes mechanisms to achieve reusable components
Measurement


Activities required to create work products such as docs
Reusability management


Manages the effects of change throughout the process
Work product preparation and production


Defines/conducts activities to ensure quality
Software configuration management


Assess work products to uncover/remove errors before next action/activity
Software quality assurance


Assess progress and maintain schedule
Defines/collects process, project, product measures that helps the project
Risk management

Assess risks that may affect the final system
6
The Process Model:
Adaptability


The framework activities will always be
applied on every project ... BUT
The tasks (and degree of rigor) for each
activity will vary based on:



the type of project
characteristics of the project
common sense judgment; concurrence of the
project team
7
Process Patterns



Process patterns define a set of activities, actions, work
tasks, work products and/or related behaviors
A template is used to define a pattern
Typical examples:






Customer communication (a process activity)
Analysis (an action)
Requirements gathering (a process task)
Reviewing a work product (a process task)
Design model (a work product)
http://www.ambysoft.com/processPatternsPage.html
8
Process Patterns – An Example
Pattern Name: Prototyping
Intent: The objective is to build a model that can be assessed iteratively by stakeholders
in an effort to identify or solidify sw requirements
Type: Phase pattern
Initial Context: The following preconditions must be met: 1. stakeholders have been
identified; 2. a mode of communication b/w stakeholders and sw team has been
established; 3. the overriding problem has been identified by stakeholders; 4. an initial
understanding of proj. scope, basic requirements, and constraints has been
developed.
Problem: Requirements are hazy or nonexistent. Stakeholders are unsure that they
need.
Solution: A description of the prototyping process is presented.
Resulting Context: A software prototype that identifies basic requirements is
approved by stakeholders.
Related Patterns: customer-communications; iterative design, …
Known Uses/Examples: Prototyping is recommended when requirements are
uncertain.
9
The Primary Goal of Any Software
Process: High Quality
Remember:
High quality = project timeliness
Why?
Less rework!
10
Two Schools of Process Models

Prescriptive process models


advocate an orderly approach to software
engineering
Agile development


Encourages early incremental delivery of
software
Stresses continuous communication between
developers and customers
11
Prescriptive Process Models




Define a distinct set of activities, actions, tasks,
milestones, and work products.
Software engineers and managers adapt a prescriptive
process model to their need
Guide a software team through a set of framework
activities that organized into a linear, incremental, or
evolutionary process flow
The work products are the programs, documents, and
data that are produced as a consequence of the
activities.
12
The Waterfall Model
Communicat ion
project init iat ion
requirement gat hering
Planning
estimating
scheduling
tracking
Modeling
analysis
design
Const ruct ion
code
t est
Deployment
delivery
support
f eedback
13
The Waterfall Model




It suggests a systematic, sequential approach to
software development.
The oldest paradigm for software engineering
Suitable for systems whose requirements are welldefined and reasonably stable.
Drawbacks:




Real projects rarely follow the sequential flow.
It is often hard for the customer to state all requirements explicitly.
A working product will not be available until late in the project time-span.
Requirement errors may not be found until they are very costly to fix.
14
The Incremental Model
increment # n
Co m m u n i c a t i o n
Pla nning
M ode ling
analy s is
des ign
Co n s t ru c t i o n
c ode
t es t
De p l o y m e n t
d e l i v e ry
fe e dba c k
deliv ery of
nt h increment
increment # 2
Co m m u n i c a t i o n
Pla nning
M ode ling
analy s is
des ign
Co n s t ru c t i o n
c ode
De p l o y m e n t
t es t
d e l i v e ry
fe e dba c k
increment # 1
deliv ery of
2nd increment
Co m m u n i c a t i o n
Pla nning
M ode ling
analy s is
des ign
Co n s t ru c t i o n
c ode
De p l o y m e n t
t es t
d e l i v e ry
fe e dba c k
deliv ery of
1st increment
project calendar t ime
15
The Incremental Model





The waterfall model applied in an iterative fashion.
Each linear sequence produces deliverable increments
of the software.
Normally core product is first delivered and
supplementary features are incrementally added.
Useful when staffing is unavailable for a complete
implementation by the project deadline.
Increments may be planned to manage technical risks
16
Rapid Application Development
Team # n
M o d e lin g
busines s m odeling
dat a m odeling
process m odeling
C o n s t r u c t io n
com ponent reuse
aut om at ic code
generat ion
t est ing
Team # 2
Com m unicat ion
Mo d eling
b u si n e ss m o d e l i n g
dat a m odeling
p ro ce ss m o d e l i n g
Planning
Co nst r uct io n
Team # 1
co m p o n e n t re u se
a u t o m a t i c co d e
g e n e ra t i o n
t e st i n g
Mode ling
De ploym e nt
int egrat ion
deliv ery
feedback
business modeling
dat a modeling
process modeling
Const r uct ion
component reuse
aut omat ic code
generat ion
t est ing
6 0 - 9 0 days
17
The RAD Model





The incremental model with a short development cycle.
Multiple RAD teams develop different components of the system in
parallel.
Short system development cycle is achieved by using a componentbased construction approach.
Suitable for systems that can be modularized in a way that enables
each major function to be completed in a short period of time.
Drawbacks:





For large systems, it requires sufficient people to form the RAD teams
If developers and customers are not committed to the rapid-fire
activities, the project would fail
If the system cannot modularized properly, it can be problematic.
It may be difficult to achieve high performance.
It may not be appropriate if technical risks are high.
18
Evolutionary Models: Prototyping
Qu ick
p lan
Quick
Com m unicat ion
plan
communication
Mo
d e l in g
Modeling
Qu i ck d e sig n
Quick design
Deployment
Deployment
De live r y
delivery &
& Fe e dback
feedback
Const r uct ion
Construction
of
of ot
prototype
pr
ot ype
19
Evolutionary Models: Prototyping

Assists the software developer and the customer to better
understand what is to be built when requirements are fuzzy.
"I know this is what I asked for, but it isn't really what I wanted."




A quick throwaway prototype for users to experiment and the
developer to understand and refine requirements based on
users’ feedback..
The customer may falsely perceive the prototype as a working
system, unwilling to continue for a complete system.
Assumptions and design architecture of the prototype may
influence implicitly the architecture of the real system.
Rarely employed for complete development cycle.
20
Evolutionary Models: The Spiral
planning
estimation
scheduling
risk analysis
communication
modeling
analysis
design
start
deployment
delivery
feedback
construction
code
test
21
Evolutionary Models: The Spiral





Risk-driven process model.
A cyclic approach for incrementally growing a system’s
degree of definition and implementation.
A set of anchor point milestones for ensuring stakeholder
commitment for feasible and mutually satisfactory solutions.
Prototyping can be employed as a risk reduction mechanism
at any stage
A good approach for large-scale systems.
22
Still Other Process Models

Component based development—systems are built by
integrating Commercial off-the-shelf (COTS) software
components. Following the following steps:
1.
2.
3.
4.
5.

Research and evaluate component-based products
Resolve component integration issues
A software architecture is designed to accommodate the
components
Components are integrated into the architecture
Comprehensive testing is conducted.
Formal methods—emphasizes the mathematical
specification of requirements
23
Still Other Process Models

Aspect-oriented software development (AOSD)

Certain concerns span the whole system architecture





High-level properties of the system: security, fault tolerance
Application of business rules
Systemic: task synchronization or memory management
AOSD is a process and methodological approach for defining,
specifying, designing, and constructing aspects.
Unified Process—a “use-case driven, architecturecentric, iterative and incremental” software process
closely aligned with the Unified Modeling Language
(UML) – Details coming soon
24
The Unified Process (UP)
Elab
o r at io n
elaboration
Incep t io n
inception
inception
co nst r uct io n
Release
soft ware increment
t r ansit io n
p r o d uct io n
25
UP Phases
UP Phases
Incept ion
Elaborat ion
Const ruct ion
Transit ion
Product ion
Workflows
Requirements
Analysis
Design
Implementation
Test
Support
Iterations
#1
#2
#n-1
#n
26
UP Work Products
Incept ion phase
Vision document
Init ial use-case model
Init ial project glossary
Init ial business case
Init ial risk assessment .
Project plan,
phases and it erat ions.
Business model,
if necessary .
One or more prot ot y pes
I nc e pt i o
n
Elaborat ion phase
Use-case model
Supplement ary requirement s
including non-funct ional
Analy sis model
Soft ware archit ect ure
Descript ion.
Execut able archit ect ural
prot ot y pe.
Preliminary design model
Rev ised risk list
Project plan including
it erat ion plan
adapt ed workflows
milest ones
t echnical work product s
Preliminary user manual
Const ruct ion phase
Design model
Sof t ware component s
Int egrat ed soft ware
increment
Test plan and procedure
Test cases
Support document at ion
user manuals
inst allat ion manuals
descript ion of current
increment
Transit ion phase
Deliv ered soft ware increment
Bet a t est report s
General user feedback
27
The Manifesto for
Agile Software Development
“We are uncovering better ways of developing
software by doing it and helping others do it.
Through this work we have come to value:
•Individuals and interactions over processes and
tools
•Working software over comprehensive
documentation
•Customer collaboration over contract
negotiation
•Responding to change over following a plan
That is, while there is value in the items on the right,
we value the items on the left more.”
Kent Beck et al
28
What is “Agility”?
Effective (rapid and adaptive) response to change
 Effective communication among all stakeholders
 Drawing the customer onto the team
 Organizing a team so that it is in control of the work
performed
Yielding …
 Rapid, incremental delivery of software

29
An Agile Process





Is driven by customer descriptions of what is
required (scenarios)
Recognizes that plans are short-lived
Develops software iteratively with a heavy
emphasis on construction activities
Delivers multiple ‘software increments’
Adapts as changes occur
30
Extreme Programming (XP)


The most widely used agile process, originally proposed
by Kent Beck
XP Planning





Begins with the creation of “user stories”
Agile team assesses each story and assigns a cost
Stories are grouped to for a deliverable increment
A commitment is made on delivery date
After the first increment “project velocity” is used to help define
subsequent delivery dates for other increments
31
Extreme Programming (XP)

XP Design





XP Coding



Follows the KIS principle (nothing less, nothing more.)
Encourage the use of CRC cards for classes relevant to the current increment.
For difficult design problems, suggests the creation of “spike solutions”—a design
prototype
Encourages “refactoring”—an iterative refinement of the internal program design
Recommends the construction of a unit test for the stories before coding
commences
Encourages “pair programming”
XP Testing


All unit tests are executed daily
“Acceptance tests” are defined by the customer and executed to assess customer
visible functionality
32
Extreme Programming (XP)
simple design
CRC cards
spike solut ions
prot ot ypes
user st ories
values
accept ance t est crit eria
it erat ion plan
ref act oring
pair
programming
Release
sof t ware increment
project velocit y comput ed
unit t est
cont inuous int egrat ion
accept ance t est ing
33
Adaptive Software Development


Originally proposed for complex systems by Jim
Highsmith
ASD — distinguishing features






Mission-driven planning
Component-based focus
Uses “time-boxing” (See Chapter 24)
Explicit consideration of risks
Emphasizes collaboration for requirements gathering
Emphasizes “learning” throughout the process
34
Adaptive Software Development

Speculation


Collaboration


Adaptive cycle planning uses initiation information to
define the set of release cycles (increments)
Team members multiply their talent and creative output
with mutual trust. (1) criticize without animosity (2)
assist without resentment (3) work as hard/harder as
others
Learning

As development progresses members learn toward the
complete cycle through focus groups, formal technical
review, and postmortems.
35
Adaptive Software Development
adapt ive cycle planning
uses mission st at ement
project const raint s
basic requirement s
Requirement s gat hering
JAD
mini-specs
t ime-boxed release plan
Release
sof t ware increment
adjust ment s f or subsequent cycles
component s implement ed/ t est ed
f ocus groups f or f eedback
f ormal t echnical reviews
post mort ems
36
Dynamic Systems Development Method


Promoted by the DSDM Consortium (www.dsdm.org)
DSDM—distinguishing features


Similar in most respects to XP and/or ASD
Nine guiding principles

Active user involvement is imperative.

DSDM teams must be empowered to make decisions.

The focus is on frequent delivery of products.

Fitness for business purpose is the essential criterion for acceptance of deliverables.

Iterative and incremental development is necessary to converge on an accurate
business solution.

All changes during development are reversible.

Requirements are baselined at a high level

Testing is integrated throughout the life-cycle.
37
Scrum


Originally proposed by Schwaber and Beedle
Scrum—distinguishing features





Development work is partitioned into “packets”
Testing and documentation are on-going as the product is
constructed
Work occurs in “sprints” and is derived from a “backlog” of
existing requirements
Meetings are very short and sometimes conducted without chairs
“demos” are delivered to the customer with the time-box allocated
38
Crystal


Proposed by Cockburn and Highsmith
Crystal—distinguishing features



Actually a family of process models that allow
“maneuverability” based on problem characteristics
Face-to-face communication is emphasized
Suggests the use of “reflection workshops” to review the
work habits of the team
39
Feature Driven Development


Originally proposed by Peter Coad et al
FDD—distinguishing features

Emphasis is on defining “features”


Uses a feature template



a feature “is a client-valued function that can be implemented in two
weeks or less.”
<action> the <result> <by | for | of | to> a(n) <object>
Add the product to a shopping cart
Display the technical spec of a product
Store the shipping info for a customer
A features list is created and “plan by feature” is conducted
Design and construction merge in FDD
40