Design decisions

Basic design questions

by daniel on May 19, 2009

Lately I was asked to help in the initial design of a new product, from ground up. The first thing we had to define was the playground, what are we going to do. My colleague didn’t have experience in design so I had to help him in the definition using a method that has worked quite well for me.

The method starts by defining the canvas or playground. The questions are:


1.     What: what is the system supposed to so?

2.     How: what are the processes to provide the functionality?

3.     How much: basic estimation of capacities / throughput.

4.     When: when do you want the solution?

The questions are related, interleaved and dependant. The available time will limit the functionality. The capacity will limit the functionality and limit the design options.


Due to the recursive nature of design, the same set of questions can be asked for a subsystem, module or component. This way, a full system can be decomposed, designed, and recomposed providing the full requirements.


The answer to these questions provide a rough definition of the playground, where the design provide the details and the flows for implementing the solution of the requirements

Even if the answers can’t be fully answered, even preliminary answers can help the communication with the relevant stakeholders.  So even if you are completely in the dark, just by having a meeting for discussing the 4 basic questions: What, How, How much and When.

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