1. A computer implemented process for application interface design comprising: entering a process diagram; creating a model from the process diagram; estimating a performance for a path in the model by a calculating a time to complete a path in a page of the model; comparing the performance to a criterion; and evaluating an element of the path by comparing the element to a rule, and, responsive to identifying a conflict between the element and the rule, displaying a recommendation to a developer for modifying the model to remove the conflict.