@techreport{R-88-05, TITLE = {Keeping and Forcing: How to Represent Cooperating Actions}, AUTHOR = {Christer B{\"a}ckstr{\"o}m}, YEAR = {1988}, NUMBER = {R-88-05}, INSTITUTION = ida, ADDRESS = idaaddr, ABSTRACTURL = {/publications/cgi-bin/tr-fetch.pl?r-88-05+abstr}, ABSTRACT = {This report presents a formalism for representing action structures, i.e. complex systems of actions going on in sequence or in parallel and possibly interfering or interacting with each other. The same formalism supports all kinds of reasoning about action structures like e.g. planning, plan projection and plan observation. Actions are characterized with five conditions expressing how they relate to the world and to other actions. It is possible to express not only when two actions are allowed to occur in parallel, but also when they are required to co-occur. Such synchronization is implicitly forced by the definitions of the actions. The conditions can also be used to implicitly define hierarchies of actions which can be used both downwards, for hierarchical planning, and upwards, for plan observation.}, IDANR = {LiTH-IDA-R-88-05}