Abstract
The estimation of project effort E and project duration D is based on several simple empirical rules (laws). The laws are almost independent although some dependencies must exist.
An example is the existence of so called inaccessible area (IA). IA is the set of pairs (D,E) that cannot appear.
IA is related to the changes of effort consumption dynamics (ECD) for tight project durations D. The widely used Rayleigh model RM of ECD does not imply the existence of IA and the behavior of project efforts for projects having (D,E) near their IA's.
RM has further deficiencies. Let $t_{max}$ be the time when effort intensity E(t) is maximal RM require that the effort E expended before $t_{max}$ is near to 0.52 E.
Another drawback is that RM implies almost no effort consumption for $t [.gt.] 3.5 t_{max}$. It therefore wrongly implies that zero defect software could be a feasible goal.
It is known that it is not true. We propose a new model M inspired by physics having no such drawbacks.
The model can be used to