ResourceIfc

The current capacity of the resource. In general, it can be 0 or greater

If a(t) is greater than zero

Checks to see if the resource is busy, has some units allocated

Checks if the resource is idle, has no units allocated

Checks to see if the resource is inactive

If c(t) is the current capacity and b(t) is the current number busy, then a(t) = c(t) - b(t) is the current number of available units. Under some capacity change situations, a(t) may be negative.

The number of busy units at any time t, b(t)