1. IL Marking Get out your CPU / Memory answers Swap with someone else
Mark each question
Discuss with each other how you would improve your marks

2. Objectives Understand the software development lifecycle
Be able to explain what commonly occurs at each stage of the software development lifecycle
Be able to identify at which stage of the software development lifecycle a given step would occur.

3. SDLC The development of software is very complex and can take years!
The purpose of the SDLC is to break the making of software down into manageable steps, that:
produces a piece of software that meets the users’ needs
is produced within budget
is finished on time

4. Problem – Mrs Morton is hungry…
What are the steps you might take to help me out in my hunger?

5. Sandwich Development Cycle
Feasibility Study
Analysis
Design
Implement
Evaluation
Maintenance

6. Software Development Life Cycle
It is possible and can it be done?
Remember TELOS
Technical – does the technology exist to do what we want to do?
Economical – does it make financial sense? Will we save money in the long run?
Legal – are there any copyright/licencing issues?
Operational – Will people be able to use it?
Schedule – Can it be made in time?

7. Sandwich Development Cycle
It is possible to make me a sandwich?
Do we have the correct equipment?
What will the costs be?
When does the sandwich need to be made by?

8. Software Development Life Cycle
What will the software need to do?
Use interviews / questionnaires / observe people / find existing documentation.
Draw diagrams that identify processes and show how data will flow around the system.
The end product is the specification and user requirements (explains what the software must do)

9. Software Development Life Cycle
Data Dictionaries
A data dictionary is used to capture what each data item looks like (data item name,
data type, any formatting needed, any restrictions on range etc). Here is an example of part of a Data
Dictionary:

10. Sandwich Development Cycle
Research needs to happen as to what sandwich fillings I like, what fillings are available.
Use questionnaires / interviews to help your research.

11. Software Development Life Cycle
The software design will include:
A detailed Data Dictionary that defines any data in the system.
Input screens/user interface
Output screens and reports
How the data will be processed: main algorithms as flow charts and pseudocode.
How the software will be tested: typically a formal test plan will be drawn up at the design stage to make sure the software is tested objectively.

12. Sandwich Development Cycle
Think about the shape of the sandwich e.g. triangles / squares?
Think about the layers of the sandwich e.g. ham then lettuce and tomato on top?

13. Software Development Life Cycle
Implementation includes the following activities:
Coding & Testing the software Writing documentation: technical documentation, for whoever has to support and maintain the software later, and a user guide
Installing the software for the user (if this software is written for a particular customer, as opposed to commercial off-the-shelf software).

14. Sandwich Development Cycle
Make the sandwich!

15. Software Development Life Cycle
Does it do what it is supposed to do?
The software must be evaluated against the original specification/User Requirement document. This is also called Acceptance Testing.
If everything works the developer can get paid!

16. Sandwich Development Cycle
Taste the sandwich and tell you what I think about it.
Do I like it?
Would I like to change it next time?
What would I take away or add?

17. Software Development Life Cycle
Corrective maintenance – fix any bugs that come up.
Adaptive maintenance – when the software needs to change to meet new requirements.
Perfective maintenance – the user might want request performance improvements or changes to how it looks to make it easier to use.
Remember CAP!

18. Sandwich Development Cycle
Clean up any crumbs that have dropped.
Put any rubbish in the bin.

19. B A C D E F G H I J Identify problems with existing data
Test the new system B A
Evaluate the new
system
Carry out a Feasibility Study C D
Maintain the new
system
Analyse the new system’s requirements E F
Implement the new system
Build the new system
Put these into order. G H
Produce Documentation for the users
Design the new system I J

20. A C D E F J G H B I System Life Cycle Answers
Identify problems with existing data
Evaluate the new system
Carry out a Feasibility Study
System Life Cycle
Answers E
Analyse the new system’s requirements
Maintain the new system F J G
Implement the new system
Design the new system
Produce Documentation for the users
Test the new system
Build the new system H B I

21. Review
Can you create a method that will help you to remember the order of the SDLC?
Song
Limmerick
Rhyme
What problems might there be with the SDLC?

22. Challenge: Waterfall Model
You have 5 minutes to find out what the waterfall model is.
And an advantage / disadvantage.
5 minutes
End

23. Waterfall Model

24. Waterfall Model Steps completed one at a time
Each step should have an output
Can go back but then the steps will need redoing
User has little impact after analysis until the evaluate stage.

25. Waterfall Model Advantages Disadvantages
Self-contained steps are easy to manage
Defined processes and output per step
Good model for managing large groups of developers working in parallel
Requirement changes mean going back to an earlier stage that had already been completed
Changes can be costly in money and time
Lack of customer involvement after Analysis means issues are not highlighted until the Evaluation

26. Challenge: Cyclical Model
You have 5 minutes to find out what the cyclical model is.
And an advantage / disadvantage.
5 minutes
End

27. Cyclical Model

28. Cyclical Model Similar to waterfall model
Knows that once a version of software has come out, then ideas for a new version are already being made taking it back to the feasibility study.

29. Cyclical Model Advantages Disadvantages
Self-contained steps are easy to manage
Defined processes and output per step
Good model for managing large groups of developers working in parallel
Maintenance, logically starts the next cycle of the process so it maps better on to the real lifecycle of a complex piece of software.
Requirement changes mean going back to an earlier stage that had already been completed
Changes can be costly in money and time
Lack of customer involvement after Analysis means issues are not highlighted until the Evaluation

30. Challenge: Spiral Model
You have 5 minutes to find out what the spiral model is.
And an advantage / disadvantage.
5 minutes
End

31. Spiral Model

32. Spiral Model Developing the software in iterative (repeating) stages
After each run through a prototype is made
Keeps refining the software
Used for larger projects

33. Spiral Model Advantages Disadvantages
Well defined steps in the process make it easy to manage
Interim prototypes highlight issues quickly so that the end product is more likely to be what the customer wants
Iterative nature of the process means changes can be easily incorporated as feedback is received
It takes time to build prototypes and get feedback, so it takes longer to get the product to the customer
Longer timescale means it costs more to develop

34. Match Up! Spiral Model Waterfall Model Cyclical Model Agile Model
A – Used for large projects, after going through each stage a prototype is made.
B – When you get to maintenance it starts the steps all over again (to develop a new version).
C – If you go back to a step you have to follow through the other steps again.
D – Where small group of developers work together, great if the requirements might change
Spiral Model
Waterfall Model
Cyclical Model
Agile Model

35. Actual Exam Question – 8 marks!

36. Way to Remember Each Model?
Can you come up with a unique way of remembering the difference between each model?

37. Remember Waterfall
Large groups of developers working at once. (large waterfall – lots of people jumping off it at once!)
Each step produces an output (like water coming out).
Steps need doing one at a time like the water going down each step in a waterfall one at a time.
Problems not highlighted until water gets to the end?

38. Remember Cyclical
Cycle Wheel goes round and a new version is created.

39. Remember Spiral Prototypes on each layer of the spiral.
Time and cost to get down the spiral

40. Questions to Answer in Book
What are the 3 stages of the maintenance stage in the SDLC?
Corrective – fix bugs
Adaptive – requirements change
Perfective – look better / work better
What happens in the feasibility study?
TELOS (Technology? Economical? Legal? Operational? Schedule?)
How do software developers carry out the analysis stage?
Questionnaires
Interview
Observe
What happens in the implementation stage?
Coding
Testing
Write documentation
Installation PC

41. Questions to Answer in Book
What is the waterfall model?
Name 3 advantages and disadvantages of the waterfall model?
What is the spiral model?
Name 3 advantages and disadvantages of the spiral model? PC

42. Further resources Revision booklet

43. Review
Can you simplify each model to 10 words?
Now 5?