Importance

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Abstract

Methods and data structures which permit information to be stored as objects in target containers and update containers. A target container defines a first state of the information, and the update container, which can point to the target container, identifies changes to the information in the first state which would be sufficient to update the first information state to a second information state. Update containers may be nested to any depth. When an application program opens an update container, the procedure searches down the chain until it finds the ultimate target container. It then creates in-memory structures for providing access to the objects and value data represented in such container. The procedure then works its way back up the chain, performing the changes on the in-memory structure, which are called for in each of the update containers. New modifications made after this process is complete, are recorded in memory, and when committed, are written out into a new update container which references the container that the application program originally opened. The changes which are identified in an update container, if they represent modifications to an object in an underlying container, refer to that object logically rather than physically. Multiple concurrent (parallel) updaters are supported, since more than one update container can refer to the same target container. Thus each updater has an independent view of the information being updated. The mechanism facilitates reconciliation of concurrent updates since it maintains a record of the changes made.

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