1. Software Life-Cycle and Models

2. Let's Define Some Terms Software Life Cycle
Software Life Cycle [Model]
Software Development Life Cycle [Model]
Software Process
Software Process Model
aka: Defined Software Process

3. What is a Software Lifecycle?
Stages of existence of software.
Each stage represents a different state of software.
Can be from developer's view or customer's view.

4. Real World Software Lifecycle
idea.
decision to implement.
initial prototype.
create a fake business case to justify writing it.
reimplement in greater detail
add requirements (because its too hard to remember what we've doing)
software + architecture design
working but buggy software
software initial release for use
iterative fix bugs and add new features

5. What is a Life Cycle Model
A model of the phases that software goes through
Serves as a guide for management of software development
Models omit some real-life complexity and detail

6. Typical Lifecycle Model
Inception of idea
vision
business case
Analysis
Design
Implementation
Acceptance
Deployment
transition
training & education
Maintenance and Support
End of Support
Retirement
end of useful life
transition or archiving
GREEN = part of the process, not life cycle

7. Is Testing Part of the Software Lifecycle?
Many people say it is.
Or, is it an activity that is part of many steps in the development process.

8. What We Want Idea Software
One of the problems with complex system design is that you cannot foresee the requirements at the beginning of the project. In many cases, where you think you can start with a set of requirements, that specifies the completely the properties of your system you end up with....
Software
source: Bruegge, Object-oriented Software Engineering

9. How it should go: Our plan of attack
Requirements
Analysis
Design
Implementation
Testing
Delivery and Installation
source: Bruegge, Object-oriented Software Engineering

10. Why the LC Model Doesn't Work
Requirements aren't complete or accurate.
even the client doesn't know precisely
Analysis and design aren't accurate.
communication issues
model not precise
Difficult to manage change...
technology changes
new requirements emerge
resource limitations
Software consists of many systems

11. Why End of Software Life?
Software doesn't really "wear out".
Some products reach "end of support" even though people are still using them.
So what causes its end-of-life?

12. Causes of Software Obsolescence
Newer product is superior
hardware changes
functionality is no longer needed

13. Causes of Software "wear out"
Code becomes too difficult to maintain or modify
No one understands the source code (key developers leave w/o documentation)
Cost of maintenance is more than customers' willingness to pay
related to first item
shrinking customer base