Tombstone diagram

A tombstone diagram is just like a picture that shows something that happened over time. Imagine drawing a line on a piece of paper, and then drawing little pictures or symbols at different points along that line. Each of those pictures or symbols represents something that happened at a specific time.

Now imagine that instead of just pictures or symbols, you use tiny gravestones or tombstones instead. Each gravestone represents something that stopped existing or stopped working at a specific time. For example, if you were making a tombstone diagram of technology, you might draw a little gravestone for every time a company stopped making a certain product, or when a computer system stopped being used.

By looking at the tombstone diagram, you can see how things have changed over time, and you can see what things have stopped working or stopped being used. It's like a way to remember or document what has happened in the past.