1. SYSC 3100 - System Analysis and Design
Basic Concepts
Software lifecycles and Requirement Engineering

2. Questions How do you build things?
How do you think software is built today?
Are they the same?

3. Objectives Describe the software life-cycle
Explain the development styles for a small selection of development models.
Waterfall V
Incremental.

4. Life cycle
A structured set of activities required to develop a software system
Specification;
Design;
Validation;
Evolution.
A software life cycle is an abstract representation of a development process. It presents a description of a process from some particular perspective.

5. Software Life Cycles A software life cycle has a number of:
Distinct activities:
“requirements”, “analysis”, “design”,
“implementation”, “testing”, “operation”
Products:
requirements, analysis, design and testing documents,
user manual, …
Rules for completing a phase and transitioning to the next phase

6. Software Life Cycles Well-known models for a software life cycle:
The Waterfall model
The V model
Incremental software development
The Rational model (Rational Unified Process)

7. The waterfall model Requirements definition System and Software Design
System’s services, constraints and goals
System and Software Design
System architecture, software system functions
Implementation and Unit Testing
Set of programs or program units
Integration and System Testing
Units and programs are integrated and tested
The main drawback of the waterfall model is the difficulty of accommodating change after the process is underway.
One phase has to be complete before moving onto the next phase.
Operation and Maintenance

8. Waterfall Model Problems
Inflexible partitioning of the project into distinct stages makes it difficult to respond to changing customer requirements.
Therefore, this model is only appropriate when the requirements are well-understood and changes will be fairly limited during the design process.
Few business systems have stable requirements.
The waterfall model is mostly used for large systems engineering projects where a system is developed at several sites.

9. Unit and Integration Testing
The V model
Requirements
Acceptance Testing
System Analysis
System Testing
Unit and Integration Testing
System Design
A variant of the Waterfall model
Implementation

10. Incremental delivery
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.

11. Incremental development

12. Incremental development advantages
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.

13. (Rational) Unified Software Development Process
A modern process model derived from the work on the UML and associated process.
Inception
is concerned with determining the scope and purpose of the project
establishes the business case for the system
Elaboration
focuses requirements capture and determining the structure/architecture of the system
develops an understanding of the problem domain
Construction: System design, programming and testing
Transition: product installation and rollout

14. 1 2 3 4 5 6 7 8 9 10 Size of square relative to time spent on workflow
Inception
Elaboration
Construction
Transition
Project Phases 1 2 3 4 5 6 7 8 9 10
Iterations within each phase
Requirements
Analysis
Design
Implementation
Test
Workflows