Representing what is needed.
WHY MODELS HELP
A diagram frequently reveals gaps that prose conceals.
WHAT USE CASES DESCRIBE
A goal a user has, and the steps to achieve it, including what can go wrong.
WHY THE FAILURE PATHS MATTER
They are where most requirements are missing.
WHAT USER JOURNEYS SHOW
The whole path a person takes, across the system and outside it.
WHAT PROCESS DIAGRAMS SHOW
The sequence of activities, and where decisions occur.
WHAT DATA MODELS SHOW
What information exists, and how it relates.
WHY THAT MATTERS EARLY
The data model is expensive to change once data exists.
WHAT STATE DIAGRAMS SHOW
What states something can be in, and what transitions are permitted.
WHY THEY ARE USEFUL
They reveal transitions nobody considered.
WHAT TO KEEP MODELS AS
Simple, and only where they add understanding.
WHAT TO AVOID
Modelling everything Models nobody reads Models that diverge from reality
WHAT TO DO WITH THEM AFTERWARDS
Keep them current, or discard them.
