Tuesday 15 June 2021

Design Rational

Design rational is the process of justifying a designers choice from their options; the euphemism "There's more than one way to skin a cat" holds very true for UX design. Oftentimes when solving a UX challenge the designer has numerous options, the trick is to pick the best one for this particular instance of this problem.

"Design rational is the articulation of various trade-offs between potential options to guide design towards the most optimal solution."

Design rational aims to understand the various options in terms of their various pros and cons and then justify the decision to pursue one particular design route over the alternatives. there are many pragmatic and theoretical approaches to selecting a design route, almost all of them are based on the articulation of design trade-offs and using those trade-offs to make a decision.

Questions, Options, and Criteria.
QOC is a methodology to facilitate systematic and principled decision making for design options. It's routed in the notion that

"A feature is represented by multiple options, which answer a particular question. Criteria help articulate the various tradeoffs between the options and guide the choice of which option to settle on."


  • Provide structure to the design space
  • Help uncover and define design alternatives


  • Are different potential solutions to the same question


  • The required and desired properties that a solution should satisfy 
  • Differ in importance and generality 
  • Help determine reasons for a decision
Criteria do not just come out of thin air, they are founded in requirements and often come from:
  • UX research, the formative work that is done with target users
  • Requirements gathering both functional and non functional
  • Accessibility constraints: visually impaired, hands free for driving, etc 
  • Usability: integration into daily routines, Privacy, social acceptability, etc
  • Previous studies: historically identify what works, established paradigms  
  • Behavioral theory: how do people act vs how they portray/believe they act
  • Common sense.
where ever your criteria come from it's important to understand they are not arbitrary and are in fact rooted in a need, when a criteria is proposed ask why? if you can't come up with a good answer then you should rethink the criteria.

By listing all of the criteria required