SOFTWARE
ENGINEERING
Lecture 4

By Mehwish Kayani
Software Process Models
The strategy to adopt software engineering as a layered
technology is referred to as Software Proc...
Linear Sequential model
Also known as the classic life cycle or waterfall
model, it suggests a systematic, sequential
appr...
Linear Sequential Model: Waterfall
Model
System/information
engineering

Requirements
Analysis

Design
Coding
Testing
Main...
Linear Sequential model
Limitations
•Real projects rarely follow the sequential flow and
changes can cause confusion.
•Thi...
Incremental Model










This is a combination of the linear sequential
model and the iterative model.
The problem...
Incremental Model
System / Information
Engineering

Analysi
s

Design

Analysi
s
Analysi
s
Analysi
s

Code

Design
Design
...
Incremental Model: Advantages
 Less

staffing is required
 Early delivery is guaranteed
 Progress of the whole project ...
Evolutionary Process Models
Software Evolves
Business and product requirements change-Creeping
requirements
Tight marke...
Prototyping


The developer and customer define the
overall objectives for the software. A quick
design focuses on what t...
Prototyping
Quick
Plan

Communication

Deployment
Delivery &
feedback

Modelling
Quick
Design

Construction
of prototype

...
Prototyping
Engineer
Product

Requirements

No
Yes

Quick
Design

Changes?
Build
Prototype

Refine
Prototype
Evaluate
Prot...
Problems with prototyping







The customer sees a working version and
expects the finished product to be available
...
Spiral Model









Boehm’s (1988) spiral model couples the iterative
nature of prototyping with the controlled and...
Spiral Model details
Spiral model is divided into a number of framework activities, named as
task regions.3-6 task regions...
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Transcript of "Software engineering leture4"

  1. 1. SOFTWARE ENGINEERING Lecture 4 By Mehwish Kayani
  2. 2. Software Process Models The strategy to adopt software engineering as a layered technology is referred to as Software Process Model Problem Definition Status Quo Technical Solution Integration
  3. 3. Linear Sequential model Also known as the classic life cycle or waterfall model, it suggests a systematic, sequential approach to software development that begins at the system level and progress through analysis, design, coding, testing and support.
  4. 4. Linear Sequential Model: Waterfall Model System/information engineering Requirements Analysis Design Coding Testing Maintenance
  5. 5. Linear Sequential model Limitations •Real projects rarely follow the sequential flow and changes can cause confusion. •This model has difficulty accommodating requirements change •The customer will not see a working version until the project is nearly complete •Developers are often blocked unnecessarily, due to previous tasks not being done
  6. 6. Incremental Model      This is a combination of the linear sequential model and the iterative model. The problem is broken into increments, and each increment is tackled as a linear sequence. Further increments can either be done after the previous ones, or can overlap with the previous ones. Incremental delivery focuses on the delivery of an operational product with each increment. Early increments are stripped-down versions of the final product.
  7. 7. Incremental Model System / Information Engineering Analysi s Design Analysi s Analysi s Analysi s Code Design Design Design Test Code Increment 1 Increment 2 Test Code Test Code Incremental model (Pressman 1997) Test Increment 3 Increment 4
  8. 8. Incremental Model: Advantages  Less staffing is required  Early delivery is guaranteed  Progress of the whole project is not delayed if one of the resources is not available for part of it
  9. 9. Evolutionary Process Models Software Evolves Business and product requirements change-Creeping requirements Tight market deadlines compels for a limited version Details of the product
  10. 10. Prototyping  The developer and customer define the overall objectives for the software. A quick design focuses on what the customer will see. From this, a prototype is constructed. The user evaluates it and improvements are made. This continues in an iterative fashion until a satisfactory product is achieved.
  11. 11. Prototyping Quick Plan Communication Deployment Delivery & feedback Modelling Quick Design Construction of prototype (Pressman, 2010)
  12. 12. Prototyping Engineer Product Requirements No Yes Quick Design Changes? Build Prototype Refine Prototype Evaluate Prototype (Pressman, 1996)
  13. 13. Problems with prototyping     The customer sees a working version and expects the finished product to be available in a short time. This puts pressure on the developer to take short cuts, at the expense of quality and maintainability. The developer may make compromises for speed. Inappropriate tools may be used or inefficient algorithms may be used, which then become integral parts of the system. If the user isn’t focused on what they want, the system may never be completed.
  14. 14. Spiral Model      Boehm’s (1988) spiral model couples the iterative nature of prototyping with the controlled and systematic aspects of the linear sequential model. Software is developed in a series of incremental releases. During the early releases, there may be just a paper model, but the system becomes increasingly more complete. There are a number of framework activities (Customer communication, Planning, Risk analysis, Engineering, Construction and release, Customer evaluation). Unlike any of the other models, this model keeps revisiting the system throughout its lifetime
  15. 15. Spiral Model details Spiral model is divided into a number of framework activities, named as task regions.3-6 task regions. Each task region has its own task sets. Planning Risk analysis Customer communicatio n Engineering Customer evaluation Construction and release
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