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CS 5150 2
Administration
Project teams
• Any announcement to class?
• People who would like to form teams?
CS 5150 3
Administration
Project teams
When you have formed your team and reached agreement with your client, please send a message to:
wya@cs.cornell.edu and afix.cs.cornell.edu
with the names of the team, the client's name, and the topic of the project.
CS 5150 5
Software Process
Fundamental Assumption:
Good processes lead to good software
Good processes reduce risk
Good processes enhance visibility
CS 5150 6
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
CS 5150 7
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
CS 5150 8
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.
CS 5150 9
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 specified in a manner that is understandable by both the client and the development staff.
CS 5150 10
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
CS 5150 11
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 components are integrated and tested against the design by the development staff as a complete system.
CS 5150 12
Process Step: Acceptance Testing and Release
Acceptance testing
The system is tested against the requirements by the client.
Delivery and release
The system is delivered to the client and released into production.
CS 5150 13
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
CS 5150 14
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
CS 5150 15
Sequence of Processes
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.
• Phased: Divide the project into a number of phases. Implement each phase in turn and put it in production immediately.
CS 5150 17
Iterative Development: Iterative Refinement (Evolutionary Development)
Concept: Initial implementation for client and user evaluation, followed by refinement until system is complete.
• Vaporware: user interface mock-up
• Throw-away software components
• Dummy modules
• Rapid prototyping
• Successive refinement
CS 5150 18
Iterative Processes: Requirements and Risk
Mistakes in the requirements are the most expensive to correct.
Requirements are hard to understand until there is an operational system, particularly with user interfaces
Create an outline system quickly, review it with clients, test it with users, improve the understanding of the requirements
Example: Integration of browser into operational system
CS 5150 19
Sequential Development:The Waterfall Model
Requirements
System design
Testing
Operation & maintenance
Program design
Implementation (coding)
Acceptance & release
Requirements
Design
Implementation
Feasibility study
CS 5150 20
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, which often requires the earlier stages to be revised.
The Waterfall Model is not enough!
CS 5150 21
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.
CS 5150 22
Modified Waterfall Model
Requirements
System design
Testing
Operation & maintenance
Program design
Implementation (coding)
Acceptance & release
Waterfall model with feedback
This is better
Feasibility study
CS 5150 23
Phased Development
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.
• User feedback can be incorporated in later phases.
CS 5150 24
Phased Development Online
When software is released online it is possible to divide it into 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 an established architecture.
It is not possible for shrink wrapped software, embedded systems, or similar environments.
CS 5150 25
Mixed Processes: User Interface Development
User interfaces have to be tested with users. This forces iterative development, even within an underlying sequential process.
A common model is to combine iterative refinement of user interfaces within an overall sequential process.
(Iteration within the steps of a sequential process is sometimes called a spiral development process.)
CS 5150 26
Examples of Mixed Processes: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 formal set of requirements. Write new compiler and run-time system incorporating graphics elements. Make minor adjustments to requirements as needed.
CS 5150 27
Modern Developments in Software Processes
Changes during the software development process are expensive.
• If the requirements are poorly understood, or expected to change, select a process that keeps flexibility. Iterative refinement, phased implementation.
• For big software systems with many inter-related components, avoid major changes to the design of a system during development. Sequential process, such as the modified waterfall model.
CS 5150 28
Modern Developments in Software Processes
Agile software development is a variant of iterative refinement that stresses rapid iterations with a flexible approach to requirement and design.
Extreme programming is an approach that concentrates on selected techniques of software development, e.g., coding by teams, design and code reviews, and typically releases software in a sequence of small phases.
CS 5150 29
Observations about Software Processes
Completed projects should have the basic process stepsbut ... 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.
CS 5150 30
CS 5150 Project Presentations: Iterative Option
Requirements
DesignImplementation
Evaluation
first presentation
second presentation
third presentation
CS 5150 31
CS 5150 Project Presentations: Sequential Option
Requirements
System design
Testing
Operation & maintenance
Program design
Implementation (coding)
Acceptance & release
1. Requirements
2. Design
3. Implementation
Feasibility study
If you follow a sequential process the three presentations should be as shown.
CS 5150 33
Project Suggestion: eCommons
Harvesting from Web sites for the Cornell academic repository
John Saylor, Cornell University Library
CS 5150 34
Project Suggestion: iPhone Application for Pet Nutrition
Stephanie Specchio, College of Veterinary Medicine
Ron DiNapoli, Cornell Information Technologies
CS 5150 35
Project Suggestion: Field of Mars
Social networking and e-commerce site for athletics and fitness
Jonathan and Aleda SchafferJohnson School, Cornell University
CS 5150 36
Project Concept: Legal Information Institute
• Spaeth database of Supreme Court statistics
• User contributed queries
Tom Bruce, Director Legal Information Institute
CS 5150 37
Project Concept: FSAE Race Car
Controller area network for FSAE race car
Cangming LiuFSAE Race Team
CS 5150 38
Project Concept: Risk Management and Public Safety
Personal Protection Equipment & Training Assessment Tool
Curtis Baker, Risk Management and Public Safety Information Services [former CS 5150 student]
CS 5150 39
Project Suggestion: Civitas electronic voting system
Civitas electronic voting system
Michael ClarksonComputer Science Department
CS 5150 40
Project Suggestions from Electrical and Computer Engineering
GPS Sensor Array ManagementBrady O'Hanlon
Aerobic Exercise MonitorJohn Belina
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