Here's a way to visualise the clustering (affinity) process used to sort large amounts of information into core themes; to enable understanding, and guide solution development. Here’s an information architecture example I whipped up.

clustering in IA

Clustering provides greater clarity and enables us to distil core themes to work with, without being caught up with too much detail.

In identifying the core functionality of an application for example, the process begins at the bottom-most row. This contains all the different functional wants and needs gathered from user requirements, business requirements, ethnographic studies and so on.

These can be clustered into say – critical functions, support functions, and nice-to-have-but-optional functions.

Further clustering may reveal two different plans. Plan A incorporates most of the critical functions, plus subsets of the support and nice-to-haves. Plan B delivers all the critical functions but none of the others.

clustering in appdev