STD extraction

As may be apparent to the reader, how an STD is extracted for an interactive software is important for user delay prediction. For example, if Calculator is modeled using only one state, which may seem like a natural model, the user delay prediction may degrade as demonstrated for the history-based model. Also, the not-so-good performance of user delay models for Go and Solitaire can be partially attributed to modeling them with a single-state STD. Adding states into the STD has the potential to improve intra-state consistency and the tradeoff between energy savings and lazy errors.