Evolving Persistent Objects in a Distributed Environment

Nestor, J.

Technical Report
CMU/SEI-87-TR-046

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This paper considers a class of objects, called incrementally mutable objects, that are intermediate between mutable and immutable objects. Intuitively, the only permitted modifications to an incrementally mutable object are those that add new information to the object while preserving existing information. Changes to incrementally mutable objects do not require central synchronization. When a network becomes partitioned, the same incrementally mutable object can be safely modified in each subnetwork. A mutable object can be modeled by a set of immutable objects that represent each value of the object over time and an incrementally mutable object that relates each immutable object to its successor. Multiple successors are permitted to represent parallel changes.

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