Requirements:the Last BottleneckBill KarwinZendCon • Santa Clara • 2010/11/3

Me

• Software developer

• C, Java, Perl, PHP, Ruby

• SQL maven

• Author of new book SQL Antipatterns

cost

the greatest single cost in producing software is

programmer time

code faster!

Tools for reducing programmer time

• Dynamic languages

• Lots of functions

• OO design

• Code reuse

• Code generation

• IDE’s

• Frameworks

• Source control

• Test automation

• Agile development

• Tools help productivity for coding and error removal

• But not so much for requirements management

Error removal is the most time-consuming part of development

Facts and Fallacies of Software Engineering, Robert L. Glass

Cost to fix a defect

Software Requirements, Karl E. WiegersCode Complete, Steve McConnell

code faster?

code less!

Front-load the project

Facts and Fallacies of Software Engineering, Robert L. Glass

managing requirements reduces project cost

so why don’t we do it?

“We practice Agile Development, so we don’t need requirements.”

Really?

Agile Manifesto?

Principle #2:

“Welcome changing requirements, even late in development.”

http://www.agilemanifesto.org/

Test-Driven Design?

“TDD is very good at detailed specification and validation, but not so good at thinking through bigger issues such as the overall design, how people will use the system, or the UI design (for example).”

Introduction to Test-Driven Design, Scott W. Amblerhttp://www.agiledata.org/essays/tdd.html

Extreme Programming?

Extreme Programming Explained: Embrace Change, Kent Beck

Coding

If you don’t code, you haven’t done anything.

Testing

If you don’t test, you don’t know when you are done

coding.

Listening

If you don’t listen you don’t know what to code

or what to test.

Design

So you can keep coding and testing and listening

indefinitely.

Scrum?

• Product Backlog: the prioritized list of desired project outcomes/features

http://www.scrumalliance.org/learn_about_scrum

Repeat for each Agile iteration

“Every time the design changes, we have to update

the requirements doc.”

“Requirements are not architecture.

Requirements are not design,nor are they interface.

Requirements are need.”

The Pragmatic Programmer: From Journeyman to Master, Andrew Hunt and David Thomas

do not dictate the implementation

in the requirements

Decoupling

• Familiar principle of OO design

• Interface vs. implementation

• Design patterns (Strategy, Bridge, etc.)

Decouple requirements from solutions

Solution 2C#, .NET

Solution 1Java, Spring

Solution 3PHP

Require-ments

☒

☑

☒

“How much detail is enough?”

“If it takes more than 15 minutes to determine what it is that you’re building, the spec wasn’t done properly.”

Really?

• Imagine your boss has a great idea

• He’s going to describe his idea to you

• You’re to code it while he’s gone

• He has to leave in 15 minutes

• Here’s his vision...

How much is enough?

• Probably a bit more than 15 minutes

• But not a whole book

• Focus on goals to satisfy, not design or implementation

“No one reads requirements docs anyway.”

• Right—if the docs aren’t helpful

• Make the docs helpful to developers

• Describe what to build, not how

SMART goals

specific

measurable

achievable

results-oriented

timely

Specific

• Be concrete; use action verbs

• Users will have an intuitive experience using our software.

• Users will be able to post textual content of 140 characters or fewer, and to search the content posted by others.

☒☑

Specific

• Also specify what the project does not need

• Support all browsers, full stop. It doesn’t matter how obscure or how old.

• Test the browser brands/versions used by 97% of the target market.

☒☑

Measurable

• Describe testable or quantifiable goals

• The web site will work at web scale.

• The web site will serve up to 10 million users; up to 10 thousand posting simultaneously; up to 500 thousand reading content stream.

☒☑

Measurable

• Measure progress as well as final result

• The whole site must have no security issues.

• Certify that each application use case is secure.☒☑

Achievable

• Set goals that are feasible and possible; stay appropriate to scope

• Our site will change the way people communicate on the web.

• Our site will let users contribute bite-sized content and search the content stream by users, by lists of users, or by tags or trends.

☒☑

Results-oriented

• Describe outputs or results—not activities

• Developers will always strive to achieve optimal performance.

• The landing page will respond in ~0.5 sec; other pages will respond in ~1.0 sec.

☒☑

Results-oriented

• Describe outputs or results—not activities

• The developers will use LAMP stack, REST architecture, scrum methodology, and git.

• Don’t dictate technology choices, design, or methodology in requirements.

☒☑

Time-related

• Use specific, realistic deadlines;include milestones, schedule

• We need our web site to go live sooner rather than later.

• Four weeks for design;three weeks for developing prototype; one week for performance testing; three weeks for refactoring;one week for final work and deployment.

☒☑

Evaluation

• Often forgotten phase

• Testing is part of this of course

• Other review of how well you met the requirements

• In Agile terms, delivery to customer

• Spell out evaluation criteria in requirements

manage requirements to develop more

efficiently

decouple requirements from solutions

be SMART

SQL Antipatterns:Avoiding the Pitfalls of Database Programming

http://www.pragprog.com/titles/bksqla/

Copyright 2010 Bill Karwin

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