TeQsim *(Temporally constrained Qsim)*, pronounced
*tek'sim*, is a qualitative simulator of dynamical systems. It is
an extension of the QSIM algorithm that incorporates behavioral information
in the form of *trajectory constraints* into the simulation process
to restrict and refine the resulting behavioral description.

Three types of trajectory constraints can be specified:

**external events**: they denote time points that mark*interesting*changes to some exogenous variable of the model; in this way references to an*absolute time-line*is made possible within the qualitative simulation;**temporal logic constraints**: a specification (using a propositional linear-time temporal logic) of the admissible trajectories of variables;**discontinuous changes**: a specification of discontinuous*jumps*of input variables.

TeQsim was used to explore the following issues:

- for focusing the qualitative simulation to interesting trajectories;
- to perform input driven qualitative simulations;
- to solve boundary conditions problems (like determining initial velocity and direction of a projectile that has to follow a certain trajectory and reach a target);
- to determine which values for parameters of a continuous feedback controller may achieve a performance satisfying certain requirements;
- to validate discrete control actions on continuous plants.

The following papers describe TeQsim:

- its theoretical foundations (get a paper submitted to a journal and a paper presented at the TIME-96 workshop);
- its overall picture (get a paper presented at AAAI-96 and and one at Qualitative Reasoning Workshop 96);
- an application to hybrid control
(get the QR'97 paper on
a hybrid system control method based on planning).

Get the slides of the QR'97 presentation of how TeQsim can be used to control a hybrid system. - its use in the development process of a qualitative model (get the QR'97 paper)
- Slides of a presentation of TeQsim.

TeQsim was developed by Daniel J. Clancy and myself. Most of the research has been performed within the Qualitative Reasoning Group at the University of Texas. TeQsim was available with the standard QSIM distribution.