On myprevious blog post, I wrote that WIP limit and Pull system are the guiding rules
that make a system stable.
I decided
to make a visual representation for Stable System, and explore the what-if
conditions for WIP limit and Pull System.
Please
note that only WIP limit or only Pull System do not guarantee system stability.
The combination of both ensures the rate of work items entering the system is the
rate of items exiting the system.
What if the WIP is not limited?
Not limiting
WIP allows new work items to enter the system, despite of work items leaving the
system. In my bar example, new bottles would be added to the bar. This makes the
rate at which work item enters the system different than the rate they exit. The
system is not stable.
What if Pull System is not being applied?
Not applying Pull System means that a work item exiting the system is not triggering a new
one to start. In my bar example, an empty whiskey bottle is removed from it, and
a new bottle is not added. This makes the rate at which work item enters the
system different than the rate they exit. The system is not stable.
