design 

rationales

irving cordova

http://irvingc.com

a personal tale

• assigned to a brand new project
• re-think architecture of an old product
• make it reach new heights!

this old project is weird

• they are using the code backwards
• this module contradicts industry standards
• this class is definitely wrong

lets write it again

• we can fix all the mistakes in one go

a few months later

• actually this old code made sense
• now I am late and behind schedule
• If only I had understood their design rationale before

capturing

design trajectories

• hard because there are too many inter relations
• Vannevar Bush proposed that a general non planar graph is needed
• the graph is hard so people use alternatives like TOC

authors attempts

failed experiment

• the author didn't achieve any great insight
• many rewrites of the ordering of the design log were needed
• one of the problems was that the end goal (a design tree) was not defined
• however insights into the process were achieved

insights into the design process

• design isn't just to satisfy requirements, but also to uncover requirements
• design isn't simply selecting from alternatives, but also realizing their existence
• the tree changes as the design changes

tree of decisions 

tree of designs

• a complete design is represented by the set of leaves in a decision tree
• in a design tree each leaf is a complete design
• a decision tree of size n yields 2^n nodes of a design tree

modular vs. 

integrated design

tools

conclusion

demo

my two cents

• a wiki page with comments enabled might be the best solution
• comments on the page might provide a forum for clarification of issues
• a wiki page is automatically versioned, and you can go back to see old designs

questions?

sources