The discrete time resource-task network (RTN) model is a generalized mixed-integer linear programming model used in scheduling optimization problems. This paper presents several extensions to the RTN that have been used at The Dow Chemical Company. One RTN extension allows for more realistic demand fulfillment: customer orders can be filled in their entirety at a distinct time point, rather than over several time periods. Modifications are proposed that allow tasks to interact not just with resources, but also with the bounds on those resources, which allows for an efficient method of modeling storage. The concept of multiple extents is introduced to extend the functionality of a single task and thereby reduce the overall size of the model and improve computation time. An alternative formulation of the RTN is also introduced in spatial rather than temporal coordinates, which allows applicability to a different class of problems such as payload optimization. (C) 2011 Elsevier Ltd. All rights reserved.