1. CS 5150 Software Engineering
Lecture 2
Software Processes

2. Administration Project teams • Any announcement to class?
• People who would like to form teams?

3. Administration Project teams
When you have formed your team and reached agreement with your client, please send a message to with the names of the team, the client's name, and the topic of the project.
Letter "l"

4. Project Suggestion: eCommons
Harvesting from Web sites for the Cornell academic repository
John Saylor, Cornell University Library

5. Project Suggestion: iPhone Applications from CIT
Registrar's services using iPhone
Ron DiNapoli, Cornell Information Technologies

6. Project Suggestion: Paperless World
Eliminate paper from credit card transactions
Keith Cowing, Johnson School, Cornell University

7. Project Concept: Student Disability Services (SDS)
Booking system for CULift service
Michele D. Fish, Student Disability Services Center for Learning & Teaching

8. Project Suggestion: Online Surveys
Online surveys for social science research
Y. Connie Yuan, Assistant Professor, Department of Communication

9. Project Suggestion: Tickets for Military
Non-profit organization to connect military members with people who have tickets to sporting events that they cannot attend
Michael Merrell, Johnson School, Cornell University

10. Project Suggestion: Tracking system for HR
A tracking and work flow system to handle the process of recruiting
Brian Martinson, Director of Human Resources, Faculty of Computer and Information Science

11. Project Suggestion: Chinese Students Studying Overseas
Robin W. Si, School of Hotel Administration, Cornell University
Support for Chinese students who wish to study in the United States or other foreign countries

12. Project Concept: Cornell Cooperative Extension
Cornell Collaborative Web Publishing Project
Raj Smith, Department of Natural Resources and Cooperative Extension

13. A Classic Book
Frederick P. Brooks, Jr. The Mythical Man Month. Addison-Wesley, 1972.

14. Software Process Fundamental Assumption:
Good processes lead to good software
Good processes reduce risk
Good processes enhance visibility

15. Variety of Software Processes
Software products are very varied...
Therefore, there is no standard process for all software engineering projects
BUT successful software development projects all need to address similar issues.
This creates a number of process steps that must be part of all software projects

16. Basic Process Steps in all Software Development
• Feasibility and planning
• Requirements
• System and program design
• Implementation and testing
• Acceptance testing and release
• Operation and maintenance
It is essential to distinguish among these process steps and to be clear which you are are doing at any given moment.
Do not confuse requirements and design

17. Process Step: Feasibility and Planning
A feasibility study precedes the decision to begin a project.
• What is the scope of the proposed project?
• Is the project technically feasible?
• What are the projected benefits?
• What are the costs, timetable?
A feasibility study leads to a decision: go or no-go.

18. Process Step: Requirements
Requirements define the function of the system from the client's viewpoint.
The requirements establish the system's functionality, constraints and goals by consultation with the client and users. They are then defined in a manner that is understandable by both the client and the development staff.

19. Process Step: System and Program Design
Design describes the system from the software developers' viewpoint
System design: Match the requirements to hardware or software systems. Establishes an overall system architecture
Program design: Represent the software system functions in a form that can be transformed into one or more executable programs

20. Process Step: Implementation and Testing
Implementation (coding)
The software design is realized as a set of programs or program units. (The software components may be written specifically, acquired from elsewhere, or modified.)
Testing
Individual components are tested against specifications.
The individual program units are integrated and tested against the design by the development staff as a complete system.

21. Process Step: Acceptance Testing and Release
The complete system is tested against the requirements by the client.
Delivery and release
The complete system is delivered to the client and released into production.

22. Process Step: Operation and Maintenance
Operation: The system is put into practical use.
Maintenance: Errors and problems are identified and fixed.
Evolution: The system evolves over time as requirements change, to add new functions or adapt the technical environment.
Phase out: The system is withdrawn from service.
This is sometimes called the Software Life Cycle

23. Sequence of Processes
Every software project will include these basic processes, in some
shape or form, but:
• They may be formal or informal
• They may be carried out in various sequences
Major alternatives
• Iterative: Go quickly through all process steps to create a rough system, then repeat them to improve the system. Iterative refinement.
• Sequential: As far as possible, complete each process step before beginning the next. Waterfall model.

24. Iterative Processes: Requirements and Risk
Mistakes in the requirements are the most expensive to correct.
-> Integration of browser into operational system
Requirements are hard to understand until there is an operational system
• Especially with user interfaces
Iterative software processes
Create an outline system quickly, review it with clients, test it with users, improve the understanding of the requirements
• Rapid prototypes
• Throw away code

25. Iterative Development: Iterative Refinement (Evolutionary Development)
Concept: Initial implementation for client and user comment, followed by refinement until system is complete.
• Vaporware: user interface mock-up
• Throw-away software components
• Dummy modules
• Rapid prototyping
• Successive refinement
Get something to evaluate as quickly as possible!

26. Iterative Refinement
Evaluation
Requirements
Design
Implementation

27. Iterative Refinement Evaluation Concurrent may be Activities
continuous
Concurrent
Activities
Initial
Version
Requirements
Outline
Description
Intermediate
Versions
Design
Implementation
Final
Version

28. Sequential Development: The Waterfall Model
Requirements
Feasibility study
Requirements
Design
System design
Implementation
Program design
Implementation (coding)
Testing
Acceptance & release
Operation & maintenance

29. Discussion of the Waterfall Model
Advantages:
• Process visibility
• Separation of tasks
• Quality control at each step
• Cost monitoring at each step
Disadvantages:
Each stage in the process reveals new understanding of the previous stages, that often requires the earlier stages to be revised.
The Waterfall Model is not enough!

30. Sequence of Processes A pure sequential model is impossible Examples:
• A feasibility study cannot create a proposed budget and schedule without a preliminary study of the requirements and a tentative design.
• Detailed design or implementation usually reveals gaps in the requirements specification.
The plan must allow for some form of iteration.

31. Modified Waterfall Model
Feasibility study
Waterfall model with feedback
This is better
Requirements
System design
Program design
Implementation (coding)
Testing
Acceptance & release
Operation & maintenance

32. Mixed Processes: Phased Development
Combine sequential and iterative elements
A simple system with basic functionality is brought quickly into production (Phase 1).
Subsequent phases are based on experience gained from users of each previous phase.
Advantages
Pay-back on investment begins soon.
Requirement are more clearly understood in developing
subsequent phases

33. Phased Development Online
When software is released online it is possible to divide it into very small phases that are developed and released in quick succession.
Example: Amazon.com divides most software development into phases of about four weeks elapsed time.
This approach is excellent for continual enhancement of a system within a well established architecture.
It is not possible for shrink wrapped software, embedded systems, or similar environments.

34. Example: Iterative Refinement + Waterfall Model:
Problem: Add graphics package to a programming environment
Phase 1: Iterative refinement
Extend current environment with a preprocessor and run-time support package. Test with users. Make several new versions until users are pleased with function. Throw the code away.
Phase 2: Modified waterfall
Use the results of Phase 1 as the basis for a detailed set of requirements. Write new compiler and run-time system incorporating graphics elements. Make minor adjustments to requirements as needed.

35. Observations about Software Processes
Completed projects should have the basic process steps
but ... the development process is always partly evolutionary.
Risk is lowered by:
• Prototyping key components
• Dividing into phases
• Following a visible software process
• Making use of reusable components
Conclusion
It is not possible to complete each step and throw it over the wall.

36. CS 501 Project Presentations: Iterative Option
Evaluation
Requirements
first presentation
second presentation
third presentation
Implementation
Design

37. CS 501 Project Presentations: Sequential Option
1. Requirements
Feasibility study
Requirements
2. Design
System design
Program design
3. Implementation
Implementation (coding)
Testing
If you follow a sequential process the three presentations should be as shown.
Acceptance & release
Operation & maintenance