Methods and apparatus of modeling the costs associated with a system that includes a plurality of components are provided. In accordance with a preferred form of the present invention, a method includes using a first and a second node of a tree structure to represent a first and a second operation associated with the system. A branch of the tree structure is also used to represent a first dependency between the first operation and the second operation. A determination may then be made as to whether a third node, in addition to the first node, represents the first operation. In the alternative, a determination may be made as to whether a second branch branches from the first operation.