Then, on the basis of probabilistic models, the software determines whether a solution exists.

If, however, a solution does not exist, the software does not give up. Instead, it suggests ways in which the planner might relax the problem constraints.

If the planner rejects the proposed amendment, the software offers another alternative. Brian Williams' group at MIT's Computer Science and Artificial Intelligence Laboratory in the US describes the software as "a better Siri" - the user-assistance application found in Apple products.

One aspect of the software that distinguishes it from previous planning systems is that it assesses risk in planning tasks such as scheduling flights or bus routes.

The team is scheduled to present their findings at the annual meeting of the Association for the Advancement of Artificial Intelligence (AAAI) Jan 25 in Austin, Texas.