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notion of sequences of user actions is not modeled. It does provide a metafacility with which
a large number of different undo strategies can be built. In (Abowd and Dix 1992), the
authors note that some implementations of undo, in order to meet user expectations, actu-
ally create and execute new actions that create interfaces states that a user will perceive as
the “undoing” of a particular effect. While the Palimpsest model provides a way to examine
the consequences of a given operation’s never having occurred, the same form of “pseudo-
inverse” strategy is still available. For some applications it may well be that deleting the text
created by an unwanted insertion is better than undoing the insertion (along with wanted
changes that are causally greater). The Palimpsest model offers powerful built-in undo op-
tions but does not in itself prescribe a policy for application undo facilities.
5.4 Summary
In this section we examined some issues in the application of the Palimpsest model to
version management and undo. We reviewed the implications of Palimpsest-style change ori-
ented editing for distributed systems implementation, and the utility of persistent address-
ing in handling fine-grained link anchor maintenance for hypertext systems.
notion of sequences of user actions is not modeled. It does provide a metafacility with which
a large number of different undo strategies can be built. In (Abowd and Dix 1992), the
authors note that some implementations of undo, in order to meet user expectations, actu-
ally create and execute new actions that create interfaces states that a user will perceive as
the “undoing” of a particular effect. While the Palimpsest model provides a way to examine
the consequences of a given operation’s never having occurred, the same form of “pseudo-
inverse” strategy is still available. For some applications it may well be that deleting the text
created by an unwanted insertion is better than undoing the insertion (along with wanted
changes that are causally greater). The Palimpsest model offers powerful built-in undo op-
tions but does not in itself prescribe a policy for application undo facilities.
5.4 Summary
In this section we examined some issues in the application of the Palimpsest model to
version management and undo. We reviewed the implications of Palimpsest-style change ori-
ented editing for distributed systems implementation, and the utility of persistent address-
ing in handling fine-grained link anchor maintenance for hypertext systems.
