Processes
Outline
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Definition of process
Type of processes
Improvement models
Example
Next steps…
Process
• Do you want to build a “dog house” or “high rise”
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• Process needed to build large /complex software systems
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Process: a set of ordered tasks
• Typical software tasks:
• What should the system do? (Requirements)
• How should the system do it? (Design)
• Writing the code… (Implementation)
• Making sure the code works (Testing)
• Using the system (Deployment)
Requirements
Design
Implementation
Testing
• Different processes order tasks differently
Deployment
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Process: Requirements
• What should the system do?
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Requirements
Customers write down what they want
Talk to customers, make diagrams
Watch users to see what’s needed
Look up requirements from standards body (e.g., medical)
Process: Design
• How should the system do it?
• Architectural design- overall structure of the system
• What components?
• How connected?
• Program design- how code should be organized
• Components => Classes and functions
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Design
Process: Implementation
• Finally, we get to write some code!!
Implementation
• May also include:
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Writing comments
Writing documentation
Helping other engineers with coding (e.g., pair programming)
Answering questions
Reading other documentation
Process: Testing
• Does the system work?
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Unit testing
System integration testing
Usability testing
Acceptance testing
…
Testing
Process: Deployment
• Using the system (aka Operation)
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Distributing code
Providing documentation and support
Debugging
Studying how the system work in practice
Adapting the system
Deployment
Outline
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Definition of process
Type of processes
Improvement models
Example
Next steps…
Types of Processes
• Waterfall
• Spiral
• Agile
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Waterfall process
Requirements analysis
Prototyping
Design
Implementation
Testing
Operation
(No prototyping in a pure waterfall process)
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Spiral Process
Draft a menu of
program designs
Analyze risk &
prototype
Draft a menu of
architecture designs
Draft a menu of
requirements
Establish
architecture
Plan
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Analyze risk &
prototype
Establish
requirements
Plan
Operation
Analyze risk &
prototype
Testing
Implementation
Establish
program design
Agile process
Do “spike” to evaluate & control risk
Customer provides “stories”
(short requirement snippets)
Prioritize
stories and plan
Operation
Write/run/modify
unit tests
Implement
System and acceptance tests
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(Agile processes are rarely this tidy in practice)
Comparing Waterfall, Spiral, Agile
Waterfall
Spiral
Agile
Emphasizes:
-Simplicity
-Traceability
-Risk management
-Exploring alternatives
-Flexibility
-Immediacy
Weakness:
Requirement/design
mistakes can be costly
Exploring alternatives
can be costly
Continual rework
can be costly
Style:
-Highly controlled
-High ceremony
-Moderately controlled
-Moderate ceremony
-Rapid & organic
-Low ceremony
Some definitions
-“traceability”: relationships between requirements and system elements are documented
-“immediacy”: getting some sort of working system to the customer as fast as possible
-“rework”: redesigning the architecture and/or refactoring the program code
-“controlled”: conformance to process is highly valued, even if it slows a project down
-“ceremony”: how much analysis, documentation, and planning is involved
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When to choose what
• Waterfall: good for smaller systems where requirements can
be fully understood before design and implementation
• Spiral: good for larger systems with vague requirements and
many alternatives for designing and coding
• Agile: good for systems where you can rapidly create
something very small but useful and then expand from there
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Outline
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Definition of process
Type of processes
Improvement models
Example
Next steps…
Improvement Models
• How to improve the system later?
• Iterative
• Get the entire system working really well
• Then add more parts
• Incremental
• Get part of the system working really well
• Then add more parts to the system
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Improvement Models
• Iterative and incremental can be mixed / matched with process
models
• Iterative Agile
• Incremental Waterfall
• Etc.
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Improvement Models: How to Choose?
• Incremental is often good when most of a system’s value is
tightly concentrated in a small number of components.
• Iterative is often good when you need to implement most of a
system before you can get much value.
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Outline
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Definition of process
Type of processes
Improvement models
Example
Next steps…
Example: Incremental Spiral Development
• Customer wants “Eco-friendly Amazon.com”
• Why pick spiral over waterfall or agile?
• Big software project
• Vague requirements
• Many alternatives
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Spiral Process
Draft a menu of
program designs
Analyze risk &
prototype
Draft a menu of
architecture designs
Draft a menu of
requirements
Establish
architecture
Plan
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Analyze risk &
prototype
Establish
requirements
Plan
Operation
Analyze risk &
prototype
Testing
Implementation
Establish
program design
Incremental Spiral: Draft Menu of Requirements
• Shopping cart
• Database of products
• Define “Eco-Friendly”
• Based on product’s “eco-friendliness”?
• Collect data from producers?
• Collect ratings from watchdog organizations?
• Collect ratings from customers?
• Eco-friendly shipping options?
• Feature to swap / trade items?
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Incremental Spiral: Review Prototypes with Customers
Paper prototypes Lightweight prototypes
Documentation
These “throwaway” prototypes are cheap to make
because they are usually not interactive.
Let’s suppose that the customer settles on eco-friendliness options based on
watchdog data.
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Incremental Spiral: Draft Menu of Architectures
Watchdog users
Shopping users
Web application
-Watchdog data input screens
- E-commerce interface
Database
PHP/Apache
Mysql
Linux
Watchdog XML feeds
Shopping users
Scrapers to read watchdog data
E-commerce interface
Database
Mysql
PHP/Apache
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Linux
Incremental Spiral: Review with Customers and/or Users
More prototypes
And now an XML mockup
And lots of analysis & discussion
about pros/cons/cost/schedule/etc.
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Documentation
Let’s suppose that the XML feed
architecture is selected, omitting
XML feeds for now (to be added
in later increment).
Incremental Spiral: Draft Menu of Program Designs
• E-commerce interface
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Make each product its own object?
Make user accounts its own object?
“Hide” database from UI code?
What should be put it “library” classes for reuse in future increments?
• E.g., XML feeds
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Incremental Spiral: Review Prototypes with Customer
Heavyweight prototypes
Documentation
These prototypes are pretty expensive to make, since they implement
some interactivity.
Therefore, they often are incorporated into the finished product
(“evolutionary” prototypes).
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Incremental Spiral: Implementation, Testing, Operation
• Wrap up increment #1
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Manually load data base with products
Finish coding UI for searching / ordering
Write / run tests
Fix bugs
Deliver code to customer
Customer tests
Deploy to public server
Test, test, test
Incremental Spiral: Increment #2, add XML feed
• Already know this is a requirement
• No need to return to requirements phase
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Return to review alternative architectures
Create a menu of program design
Prototype and review
Implement, test, send to customer
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Incremental Spiral: Increment #3
Pay attention to users, discover new requirements Spiral, spiral, spiral
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Outline
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Definition of process
Type of processes
Improvement models
Example
Next steps…
Next steps…
• Finish your Vision Statement Overview!
• Finalize your team
• Be ready to explain Waterfall, Spiral, and Agile development
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Definition
Pros / cons of each
Explain when to use, and WHY
When NOT to use…
• Next time: Requirements
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