The door to the Computer Science Building at Rochester

The fact that "actions" (operator instances) are explicitly represented by formulae is one of the main features of the language PDDL-K.

The flexibility deriving from this fact is illustrated by the simple example in this directory, borrowed from

J. F. Allen, Temporal Reasoning and Planning, in Allen, Kautz, Pelavin, and Tenenberg (editors), Reasoning about Plans, Morgan Kaufmann Publishers, 1991, pages 1-68.
In order to open the door to the Computer Science Building at Rochester, both hands must be used: a spring lock must be held open with one hand, while the door is pulled open with the other hand. Unless the lock is held open, it snaps shut.

This is an example where not only do actions have a duration, that must be represented, but also the effect of two actions performed together is different from the sum of their effects. The problem is not easily and naturally representable in STRIPS-like planning languages.

In order to run the example, simply call: pdk rochester