Chapter 2 modeling the process and life-cycle

1
Shari L. Pledger and Joanne M. Atlee (2014): Software Engineering: Theory and Practice, 4th Edition
Modeling the
Process and Life
Cycle
Chapter 2
Abdisalam Issa-Salwe
Department of Computer Science
Faculty of Information Science and Technology
East Africa University
Department of Computer Science, Faculty of Information Science and Technology, East Africa University
Contents
2.1 The Meaning of Process
2.2 Software Process Models
2.3 Tools and Techniques for Process
Modeling
2.4 Practical Process Modeling
2.5 Information System Example
2.6 What this Chapter Means for You

2
Chapter 2 Objectives
 What we mean by a “process”
 Software development products,
processes, and resources
 Several models of the software
development process
 Tools and techniques for process
modeling
 A process: a series of steps involving activities,
constrains, and resources that produce an
intended output of some kind
 A process involves a set of tools and techniques

3
Process Characteristics
 Prescribes all major process activities
 Uses resources, subject to set of constraints (such as
schedule)
 Produces intermediate and final products
 May be composed of subprocesses with hierarchy or
links
 Each process activity has entry and exit criteria
 Activities are organized in sequence, so timing is clear
 Each process guiding principles, including goals of
each activity
 Constraints may apply to an activity, resource or
product
The Importance of Processes
 Impose consistency and structure on a set
of activities
 Guide us to understand, control, examine,
and improve the activities
 Enable us to capture our experiences and
pass them along

4
Reasons for Modeling a Process
 To form a common understanding
 To find inconsistencies, redundancies,
omissions
 To find and evaluate appropriate activities for
reaching process goals
 To tailor a general process for a particular
situation in which it will be used
Software Life Cycle
 When a process involves building a software, the
process may be referred to as software life cycle
Requirements analysis and definition
System (architecture) design
Program (detailed/procedural) design
Writing programs (coding/implementation)
Testing: unit, integration, system
System delivery (deployment)
Maintenance

5
Software Development Process Models
 Waterfall model
 V model
 Prototyping model
 Operational specification
 Transformational model
 Phased development: increments and iteration
 Spiral model
 Agile methods
Waterfall Model
 One of the first process development models
proposed
 Works for well understood problems with
minimal or no changes in the requirements
 Simple and easy to explain to customers
 It presents
a very high-level view of the development
process
sequence of process activities
 Each major phase is marked by milestones and
deliverables (artifacts)

6
Waterfall Model (continued)
Waterfall Model (continued)
 There is no iteration in waterfall model
 Most software developments apply a great many
iterations

7
Sidebar 2.1 Drawbacks of The Waterfall Model
 Provides no guidance how to handle changes to
products and activities during development
(assumes requirements can be frozen)
 Views software development as manufacturing
process rather than as creative process
 There is no iterative activities that lead to
creating a final product
 Long wait before a final product
Waterfall Model with Prototype
 A prototype is a partially developed product
 Prototyping helps
developers assess alternative design
strategies (design prototype)
users understand what the system will be like
(user interface prototype)
 Prototyping is useful for verification and
validation

8
Waterfall Model with Prototype (continued)
 Waterfall model with prototyping
V Model
 A variation of the waterfall model
 Uses unit testing to verify procedural design
 Uses integration testing to verify architectural
(system) design
 Uses acceptance testing to validate the
requirements
 If problems are found during verification and
validation, the left side of the V can be re-
executed before testing on the right side is re-
enacted

9
V Model (continued)
Prototyping Model
 Allows repeated investigation of the
requirements or design
 Reduces risk and uncertainty in the
development

10
Operational Specification Model
 Requirements are executed (examined) and
their implication evaluated early in the
development process
 Functionality and the design are allowed to be
merged
Transformational Model
 Fewer major development steps
 Applies a series of transformations to change a
specification into a deliverable system
Change data representation
Select algorithms
Optimize
Compile
 Relies on formalism
 Requires formal specification (to allow
transformations)

11
Transformational Model (continued)
Phased Development: Increments and Iterations
 Shorter cycle time
 System delivered in pieces
enables customers to have some functionality
while the rest is being developed
 Allows two systems functioning in parallel
the production system (release n): currently
being used
the development system (release n+1): the
next version

12
(continued)
(continued)
 Incremental development: starts with small functional
subsystem and adds functionality with each new release
 Iterative development: starts with full system, then
changes functionality of each subsystem with each new
release

13
(continued)
 Phased development is desirable for several
reasons
Training can begin early, even though some
functions are missing
Markets can be created early for functionality
that has never before been offered
Frequent releases allow developers to fix
unanticipated problems globally and quickly
The development team can focus on different
areas of expertise with different releases
Spiral Model
 Suggested by Boehm (1988)
 Combines development activities with risk
management to minimize and control risks
 The model is presented as a spiral in which
each iteration is represented by a circuit around
four major activities
Plan
Determine goals, alternatives and constraints
Evaluate alternatives and risks
Develop and test

14
Spiral Model (continued)
Agile Methods
 Emphasis on flexibility in producing software quickly and
capably
 Agile manifesto
 Value individuals and interactions over process and
tools
 Prefer to invest time in producing working software
rather than in producing comprehensive documentation
 Focus on customer collaboration rather than contract
negotiation
 Concentrate on responding to change rather than on
creating a plan and then following it

15
Agile Methods: Examples of Agile Process
 Extreme programming (XP)
 Crystal: a collection of approaches based on the
notion that every project needs a unique set of
policies and conventions
 Scrum: 30-day iterations; multiple self-
organizing teams; daily “scrum” coordination
 Adaptive software development (ASD)
Agile Methods: Extreme Programming
 Emphasis on four characteristics of agility
Communication: continual interchange
between customers and developers
Simplicity: select the simplest design or
implementation
Courage: commitment to delivering
functionality early and often
Feedback: loops built into the various
activities during the development process

16
Agile Methods: Twelve Facets of XP
 The planning game
(customer defines value)
 Small release
 Metaphor (common vision,
common names)
 Simple design
 Writing tests first
 Refactoring
 Pair programming
 Collective ownership
 Continuous integration
(small increments)
 Sustainable pace (40
hours/week)
 On-site customer
 Coding standard
Sidebar 2.2 When Extreme is Too Extreme?
 Extreme programming's practices are
interdependent
A vulnerability if one of them is modified
 Requirements expressed as a set of test
cases must be passed by the software
System passes the tests but is not what the
customer is paying for
 Refactoring issue
Difficult to rework a system without degrading
its architecture

17
Sidebar 2.3 Collections of Process Models
 Development process is a problem-solving activity
 Curtis, Krasner, and Iscoe (1988) performed a field
study to determine which problem-solving factors
to captured in process model
 The results suggest a layered behavioral model as
supplement to the traditional model
 Process model should not only describe series of
tasks, but also should detail factors that contribute
to a project's inherent uncertainty and risk
 Notation depends on what we want to
capture in the model
 The two major notation categories
Static model: depicts the process
Dynamic model: enacts the process
2.3 Tools and Techniques for Process
Modeling

18
• Element of a process are viewed in terms of
seven types
– Activity
– Sequence
– Process model
– Resource
– Control
– Policy
– Organization
• Several templates, such as an Artifact Definition
Template
2.3 Tools and Techniques for Process Modeling
Static Modeling: Lai Notation
Static Modeling: Lai Notation (continued)
 The process of starting a car

19
Static Modeling: Lai Notation (continued)
 Transition diagram illustrates the transition for a
car
• Enables inaction of process to see what
happens to resources and artifacts as activities
occur
• Simulate alternatives and make changes to
improve the process
• Example: systems dynamics model
Dynamic Modeling

20
• Introduced by Forrester in the 1950's
• Abdel-Hamid and Madnick applied it to software
development
• One way to understand system dynamics is by
exploring how software development process
affects productivity
Dynamic Modeling: System Dynamics
Dynamic Modeling: System Dynamics (continued)
 Pictorial presentation of factors affecting productivity
 Arrows indicate how changes in one factor change
another

21
Dynamic Modeling: System Dynamics (continued)
 A system
dynamic
model
containing
four major
areas
affecting
productivity
Sidebar 2.4 Process Programming
 A program to describe and enact the process
 Eliminate uncertainty
 Basis of an automated environment to produce
software
 Does not capture inherent variability of underlying
development process
 Implementation environment, skill, experience,
understanding the customer needs
 Provides only sequence of tasks
 Gives no warning of impending problems

22
Marvel Case Studies
 Uses Marvel process language (MPL)
 Three constructs: classes, rules, tool envelopes
 Three-part process description
rule-based specification of process behavior
object-oriented definition of model’s
information process
set of envelopes to interface between Marvel
and external software tools
Marvel Case Studies (continued)
 Involved two AT&T networks
network carried phone calls
signalling network responsible for routing calls
and balancing the network load
 Marvel was used to describe the signalling
fault resolution

23
Marvel Case Studies (continued)
 Signalling Fault Resolution Process
Example of Marvel Commands
TICKET:: superclass ENTITY
status : (initial, open, referred_out, referral_done,
closed, fixed) = initial;
diagnostics : (terminal, non_terminal, none) = none;
level : integer;
description : text;
referred_to : link WORKCENTER;
referrals : set_of link TICKET;
process : link PROC_INST;
end
diagnose [?t: TICKET]:
(exists PROC_INST ?p suchthat (linkto [?t.process ?p]))
:
(and (?t.status = open}(?t.diagnostics = none))
{TICKET_UTIL diagnose ?t.Name}
(and (?t.diagnostics = terminal)
(?p.last_task = diagnose)
(?p.next_task = refer_to_WC3));
(and (?t.diagnostics = non_terminal)
(?p.last_task = diagnose)
(?p.next_task = refer_to_WC2));
Class
definition
for trouble
tickets
Rulefor
diagnosing
ticket

24
Desirable Properties of Process Modeling Tools and
Techniques
 Facilitates human understanding and
communication
 Supports process improvement
 Supports process management
 Provides automated guidance in performing the
process
 Supports automated process execution
2.5. Information System Example
Piccadilly Television Advertising System
 Needs a system that is easily maintained
and changed
 Requirements may change
Waterfall model is not applicable
 User interface prototyping is an advantage
 There is uncertainty in regulation and
business constraints
Need to manage risks
 Spiral model is the most appropriate

25
2.6 What this Chapter Means for You
 Process development involves activities,
resources, and product
 Process model includes organizational,
functional, behavioral and other perspectives
 A process model is useful for guiding team
behavior, coordination and collaboration
Reference
Shari L. Pledger and Joanne M. Atlee
(2014): Software Engineering: Theory and
Practice, 4th Edition

26
Group discussion
Group 1: Discuss the Meaning of
Software Process Models using
Waterfall Model with Prototype
Group 2: Discuss and analyze the
tools and techniques for Process
Modeling
Group 3: Software Process Models
using Spiral Model

Chapter 2 modeling the process and life-cycle

More Related Content

What's hot (19)

Similar to Chapter 2 modeling the process and life-cycle (20)

More from Taibah University, College of Computer Science & Engineering (20)

Recently uploaded (20)

Chapter 2 modeling the process and life-cycle