First, let's think about the problem of showing open task counts over time. As we're only interested in the number of open tasks at any given time, we can use a model where we put all tasks onto a single timeline, and where we are only concerned with the events of tasks being created or completed. Let's look at the following illustration to get a better understanding of the problem:
An illustration that shows how we can represent all task timelines on a single timeline, using the created and completed events. The created events count as +1, while the completed events count as -1
The lower arrow is a representation of all ...
