CS251 – Software Engineering
Lecture 21
Process and Life Cycle
‫حكمة اليوم‬
‫‪ .1‬أفلم يسيروا في األرض فتكون لهم‬
‫قلوب يعقلون بها أو آذان يسمعون‬
‫بها‬
‫‪.2‬فإنها ال تعمى األبصار ولكن تعمى‬
‫القلوب التي في الصدور‬
Assessment
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Midterm exam (5%)
Project (15% = 5 + 5 + 5 + 1 + Bonus)
Quizzes (10 + 1%)
Lab (5 + 1%)
A1 (5%)
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Lecture Outline
• SW Lifecycle
• SW Process Models
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Requirement
Software
Configuration
Management
Process Models
Software Process
Where are we now?
Analysis
Design
Implement
Testing
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Requirement
Software
Configuration
Management
Process Models
Software Process
Where are we now?
Analysis
Design
Implement
Testing
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1. Software Life Cycle
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Conception
Feasibility Study / Domain Analysis
Requirements’ Gathering
Overall Design
Detailed Design
Development (Coding, Programming)
Testing (Unit, Integration, Acceptance)
Deployment / Training
Maintenance and Evolution
Process of Building a House
Same life cycle
Different Process
Software Life Cycle
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Conception
Feasibility Study / Domain Analysis
Requirements’ Gathering
Overall Design
Detailed Design
Development (Coding, Programming)
Testing (Unit, Integration, Acceptance)
Deployment / Training
Maintenance and Evolution
Important Terms
• Software life-cycle
– Phases
– Development cycle and evolution cycle
• Software process
– Discipline, activities, roles, and artifacts
• Iterations
– Milestones
Software Life Cycle
(As in RUP)
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Conception
Feasibility Study / Domain Analysis
Requirements’ Gathering
Overall Design
Detailed Design
Development (Coding, Programming)
Testing (Unit, Integration, Acceptance)
Deployment / Training
Maintenance and Evolution
Phases of the Development
Cycle
Inception
Elaboration
Construction
Transition
T I M E
Inception - Define the scope of project
Elaboration - Plan project, specify features, baseline system
Construction - Build the product
Transition - Transition the product into end user community
Software Process
• The set of activities and associated results
that produce a software product.
• Four fundamental process activities:
– Software Specification
– Software Development
– Software Validation
– Software Evolution
• Can be organized in different ways,
described at varying level of details →
different software development process
models
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2. SE Process
• A software process model describes the
activities performed to produce a software,
the order of these activities, the roles
responsible of them and the deliverables
produced from each activity.
• The distinction between SDLC and SP is a
not clear cut.
1. Waterfall Model
• Requirements – defines
needed information, function,
behavior, performance and
interfaces.
• Design – data structures,
software architecture, interface
representations, algorithmic
details.
• Implementation – source
code, database, user
documentation, testing.
Waterfall Strengths
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Easy to understand, easy to use
Provides structure to inexperienced staff
Milestones are well understood
Sets requirements stability
Good for management control (plan, staff, track)
Works well when quality is more important than
cost or schedule
Waterfall Deficiencies
• All requirements must be known upfront
• Deliverables created for each phase are
considered frozen – inhibits flexibility
• Can give a false impression of progress
• Does not reflect problem-solving nature of
software development – iterations of phases
• Integration is one big bang at the end
• Little opportunity for customer to preview the
system (until it may be too late)
When to use the Waterfall Model
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Requirements are very well known
Product definition is stable
Technology is understood
New version of an existing product
Porting an existing product to a new platform.
2. Incremental SDLC Model
• Construct a partial
implementation of a total
system
• Then slowly add increased
functionality
• The incremental model
prioritizes requirements of the
system and then implements
them in groups.
• Each subsequent release of
the system adds function to the
previous release, until all
designed functionality has
been implemented.
Incremental Model Strengths
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Develop high-risk or major functions first
Each release delivers an operational product
Customer can respond to each build
Uses “divide and conquer” breakdown of tasks
Lowers initial delivery cost
Initial product delivery is faster
Customers get important functionality early
Risk of changing requirements is reduced
Incremental Model
• Each increment is a mini-waterfall.
8/1/2017
CPSC-4360-01, CPSC-5360-01,
Lecture
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Incremental Model Weaknesses
• Requires good planning and design
• Requires early definition of a complete and
fully functional system to allow for the
definition of increments
• Well-defined module interfaces are
required (some will be developed long
before others)
• Total cost of the complete system is not
lower
When to use the Incremental Model
• Risk, funding, schedule, program complexity, or
need for early realization of benefits.
• Most of the requirements are known up-front but
are expected to evolve over time
• A need to get basic functionality to the market
early
• On projects which have lengthy development
schedules
• On a project with new technology
3. Spiral SDLC Model
• Adds risk
analysis, and
prototyping to the
waterfall model
• Each cycle
involves the same
sequence of steps
as the waterfall
process model
Spiral Quadrant
Determine objectives, alternatives and constraints
• Objectives: functionality, performance,
hardware/software interface, critical success factors, etc.
• Alternatives: build, reuse, buy, sub-contract, etc.
• Constraints: cost, schedule, interface, etc.
Spiral Quadrant
Evaluate alternatives, identify and resolve risks
• Study alternatives relative to objectives and constraints
• Identify risks (lack of experience, new technology, tight
schedules, poor process, etc.
• Resolve risks (evaluate if money could be lost by
continuing system development
Spiral Quadrant
Develop next-level product
• Typical activites:
– Create a design
– Review design
– Develop code
– Inspect code
– Test product
Spiral Quadrant
Plan next phase
• Typical activities
– Develop project plan
– Develop configuration management plan
– Develop a test plan
– Develop an installation plan
Spiral Model Strengths
• Provides early indication of insurmountable
risks, without much cost
• Users see the system early because of rapid
prototyping tools
• Critical high-risk functions are developed first
• The design does not have to be perfect
• Users can be closely tied to all lifecycle steps
• Early and frequent feedback from users
• Cumulative costs assessed frequently
Spiral Model Weaknesses
• Time spent for evaluating risks too large for small or lowrisk projects
• Time spent planning, resetting objectives, doing risk
analysis and prototyping may be excessive
• The model is complex
• Risk assessment expertise is required
• Spiral may continue indefinitely
• Developers must be reassigned during non-development
phase activities
• May be hard to define objective, verifiable milestones
that indicate readiness to proceed through the next
iteration
When to use Spiral Model
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When creation of a prototype is appropriate
When costs and risk evaluation is important
For medium to high-risk projects
Long-term project commitment unwise because
of potential changes to economic priorities
Users are unsure of their needs
Requirements are complex
New product line
Significant changes are expected (research and
exploration)
4. Agile SDLC’s
• Speed up or bypass one or more life cycle
phases
• Usually less formal and reduced scope
• Reduce documentation
• Embed quality activities in the
development process
• Used for time-critical applications
Some Agile Methods
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Adaptive Software Development (ASD)
Feature Driven Development (FDD)
Crystal Clear
Dynamic Software Development Method
(DSDM)
• Rapid Application Development (RAD)
• Scrum
• Extreme Programming (XP)
Example SPs
– Rational Unified Process
– Scrum (Will be covered by Amr Samir)
– Remember, a SW Development Process
defines: activities (or Tasks), their
order, roles and deliverables (or Work
Products or artifacts).
1. Rational Unified Process
(RUP)
• RUP is an iterative software development
process framework by the Rational Software
Corporation, a division of IBM.
• It is not a single concrete prescriptive
process, but rather an adaptable process
framework, intended to be tailored.
• Organizations and software project teams will
select the elements of the process that are
appropriate for their needs.
UPEDU Is a version of RUP
Phases
Process Workflows
Inception Elaboration Construction
Transition
Business Modeling
Requirements
Analysis & Design
Implementation
Test
UPEDU
Deployment
Supporting Workflows
Config & Change Mgmt
Project Management
Environment
http://www.upedu.org/
Weight of Disciplines in Iteration Varies
Life Cycle Phases
Inception Elaboration Construction
Transition
Engineering Workflows
Requirements
Analysis & Design
Implementation
Test
Supporting Workflows
Configuration & Change Mgmt
Project Management
ITERATION A
ITERATION E
Artifacts Evolve in the Develop. Cycle
Inception
M R D
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Elaboration
M R D
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Construction
Transition
M R D
M R D
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Management artifacts
Requirements artifacts
Design artifacts
Implementation artifacts
An iteration is a distinct sequence of activities with an
established plan and evaluation criteria resulting in an
modified artifacts
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UPEDU Roles
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• Project Manager
Analyst
• Reviewer
Designer
• Any other Stakeholder
Implementer
Integrator
Tester
Change Control Manager
Configuration Manager
UPEDU
Implementation
Discipline:
Activities
UPEDU Implementation
Discipline: Artifacts
UPEDU Implementation
Discipline: Activities
2. Scrum
• Watch Amr Samir’s video under Acadox (11
min.)
• Very important and very nice explanation of
Scrum.
• Will com in exam
Reviewing Course Objectives1
• Teaching students the disciplined approach to
engineering software systems.
• Educating the students about the cost of
software failures and the importance of software
engineering.
• Training the students on applying engineering
practices in software development.
• Introducing learners to the Software Engineering
Body of Knowledge.
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Course Objectives2
• Training them on the basics of software
requirements engineering, modeling, and
design, construction and configuration and
process management.
• Training the students on system modeling using
UML.
• Training students on teamwork.
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Course Objectives3
• Coders - Can pretty much figure out it. It'll work, but
it won't be pretty.
• Hackers - usually low level folks, skillful, with
detailed understanding of some area deeply, often
scarily deeply.
• Programmer - Write code and understand
algorithms. Often work alone and well.
• Software Engineer - Are the best generalists, can
use lots of different systems and languages and get
them to talk to each other. Are true and broad
professionals, work with people, and communicate
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well.
How to Study
• Lectures (slides and videos and code)
• Readings
• Quizzes + Lecture Practice
• Labs + Sections
• Previous exams and questions
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