Rummel, Jeffrey L.; Walter, Zhiping; Dewan, Rajiv; & Seidmann, Abraham
European Journal of Operational Research, Vol. 161 Issue 3, p. 683-703

There is a long history of modeling projects to meet time and cost objectives. Most of these models look at adjusting the level of resources available to the project in order to crash the time required to complete certain activities. These models usually take the activities and the graph structure of the project as given and fixed, but in practice there is often significant discretion in how activities are defined. This is especially important when there are information flows and time delays associated with the hand-off between an activity and its successor. This paper models the choice of how to meet the time and cost objectives through combining multiple activities into one while maintaining the original activity precedence relationships. A mixed-integer linear programming model is developed for the problem, and an implicit enumeration and a tabu search heuristic are tested with a suite of problem examples.