Schedules in the polyhedral model, both those that represent the original execution order and those produced by scheduling algorithms, naturally have the form of a tree. Generic schedule representations proposed in the literature encode this tree structure such that it is only implicitly available. Following the internal representation of isl, we propose to represent schedules as explicit trees and further extend the concept by introducing different kinds of nodes. We compare our schedule trees to other representations in detail and illustrate how they have been successfully used to simplify the implementation of a non-trivial polyhedral compiler.