A new conceptual model for interactive user recovery and command reuse facilities

This paper generalises approaches to modelling an undo facility for interactive systems into a comprehensive user recovery and command reuse facility. It separates different undoing actions into distinct undoing functions and incorporates redoing capability in a more general command reuse capacity. Four adequacy criteria for such a facility are proposed and a general model is developed to meet these requirements. Partial, patterned and repetitive undoing and redoing actions are allowed on simple, complex and meta commands. The model subsumes the functionality of prior models.