Extracting and Using Relative Duration Information in Pure Qualitative Simulation

We show that qualitative simulation algorithms can make better use of their input to deduce significant amounts of information about the relative lengths of the time intervals in their output behavior predictions. Simple techniques employing concepts like symmetry and periodicity, and comparison of the circumstances during multiple traversals of the same interval can enable the reasoner to build a list of facts representing the deduced information about relative durations. These facts are used by a new filter, which eliminates proposed spurious behaviors leading to inconsistent duration data. Surviving behaviors are annotated with richer descriptions of the qualitative properties of system variables, in addition to the extracted relative duration information