cs 5150 1 cs 5150 software engineering lecture 2 software processes 1
TRANSCRIPT
CS 5150 1
CS 5150 Software Engineering
Lecture 2
Software Processes 1
CS 5150 2
Underclassmen: be paired with an upperclassman mentor!Upperclassmen: mentor an underclassman and/or have a PhD/MEng
mentor!
To find a mentor or to be a mentor:Fill out a questionnaire to specify your preferences--
send an email to [email protected] for the links.
ACSU Bowling /Mentor-Mentee Matching Event: 9/8 at Helen Newman!
(*please also fill out the questionnaire)Time: 9/8, 7-9 PM
Location: Helen Newman Bowling Alley (in the basement of HNL)FREE pizza and soda will be served!
ACSU is initiating a peer mentoring program
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Independent Research in Computer Science & Information Science
The Web Lab applies supercomputing methods to analyze very large collections of text. See http://weblab.infosci.cornell.edu/. It uses MapReduce programming and the Hadoop distributed file system on a large Linux cluster.
Projects for fall 2010:
• Studying how the .gov domain changes over time.
• Building indexes to very large collections of digitized books.
If you are interested, come to a meeting on Tuesday at 4:00 p.m. in the Information Science building, 301 College Avenue.
The Web Lab
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Administration
Project teams
• Any announcement to class?
• People who would like to form teams?
Project Suggestions on the web site
Entrepreneurship experiment
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Administration
Project teams
When you have formed your team and reached agreement with your client, please send a message to:
[email protected] and [email protected]
with the names of the team, the client's name, and the topic of the project.
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Software is Risky
Most software development projects have major problems
Problems
Does not work as expected
Over budget
Late delivery
Much of software is wasted (perhaps 50% is never used )
Never used
Does the wrong thing
Users dislike to use it
There are no customersetc.
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Software is Risky
What is the penalty to the client if software is:
late?over budget?does not work or full of bugs?
Examples of risk:
car anti-lock brakes (no bugs allowed)web browser in cell phone (no delays in release allowed)
Failures of software development projects can bankrupt companies
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Software is Risky
Most software projects fail because the software developers build the wrong software!
• Understand what the client, the customer, and the users expect of the software
• As a developer, provide technical insights and suggestions, but remember:
Client satisfaction and customer acceptance are the primary measures of success in a software project.
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Minimizing Risk: Incremental Development with Frequent Releases
Recent approaches to software development minimize risk by emphasizing frequent delivery of working software (weeks rather than months).
•Client, customers, and users can evaluate the developers' work.
•Opportunities to adapt to changing circumstances.
This is one of the basic principles of Agile Software Development.
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The Three-way Trade-off
Competing goals
Every software project has a trade-off between:
Functionality Resources (cost) Timeliness
What is important to the person who is paying?
Example:
Start-up companies: Are there real customers who will pay for the product?
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Minimizing Risk: Relationship with the Client
• Feasibility studies (whether to begin a project).
• Separation of requirements (what the client wants) from design (how the developers meet the requirements).
• Milestones (how the developers report or demonstrate progress to the clients) and releases.
• Acceptance (how the client tests that the software meets the requirements) and user testing.
• Handover (ensuring that the client receives a package that can be operated and maintained over a long time period).
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Minimizing Risk: Visibility
The people who take the responsibility must know what is happening
• Managers
Must rely on others for reports of progress or difficulties
• Software Developers
Have difficulty evaluating progress Optimistic
Consider reporting a waste timeetc.
Working software provides excellent visibility.
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Teams
Most software development is by teams
• Effectiveness of team determines success
Most large software projects are built on older ones
• It is rare to start a new suite of programs from scratch
• Building on the work of others is a fundamental skill of software development
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Observations about Big Projects
• A CS 5150 project is about 0.3 person/years. A big project may be 100 to 10,000+ person years.
• Every important program is written by many people, who are constantly changing.
• Before a big project is completed the requirements have changed many times.
• No large system is ever complete.
A CS 5150 project is about the size of a single increment in a production Agile process.
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Software Process
Fundamental Assumption:
Good processes lead to good software
Good processes reduce risk
Good processes enhance visibility
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Heavyweight and Lightweight Software Development
In a heavyweight process, the development team works through the entire development cycle slowly and systematically, with the aim of delivering a complete software product with minimal changes and revision.
Example: the Modified Waterfall Model
In a lightweight process, the development team releases working software in small increments, and develops the plans incrementally, based on experience.
Example: Agile Software Development
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Heavyweight and Lightweight Methodologies
Heavyweight Lightweight
Processes and tools Individuals & interactions
Documentation Working software
Contract negotiation Customer collaboration
Following a plan Responding to change
Based on the Manifesto for Agile Software Development: http://agilemanifesto.org/
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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 should be part of all software projects
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Basic Process Steps in all Software Development
• Feasibility and planning
• Requirements
• System and program design
• Implementation
• Acceptance and release
• Operation and maintenance
In a lightweight process, these steps are repeated with each increment