1. A method for determining a generic numerical delay model for a library cell type, the method comprising: receiving a set discretized delay models, wherein each discretized delay model corresponds to a timing arc of a library cell of the library cell type, and wherein each discretized delay model is capable of being represented by a set of points in a multi-dimensional space, the multi-dimensional space including an output loading dimension, an input transition dimension, an output delay dimension, and an output transition dimension; determining a set of specific numerical delay models based on the set of discretized delay models; and determining, by computer, the generic numerical delay model for the library cell type based on at least a subset of specific numerical delay models.