# Tech Report CS-92-59

## Supporting Reactive Planning Tasks on an Evolving Multidatabase

### Abstract:

In this paper we discuss our open nested multidatabase transaction model for multidatabases called {\em Interactions}. Interactions sit above a layer that provides atomic, serializable global multidatabase transactions. This model provides additional support for {\em planning applications}, which are long-running applications that may need to respond to changes in the underlying evolving multidatabase.

We begin by describing Interactions and the multidatabase architecture that they run on. We then discuss synchronization of Interactions. We describe the nature of {\em events}, which the applications can use to monitor changes in the information in the multidatabase. When relevant events occur, we define how they are detected and how to respond to them. This response usually involves semantically undoing part of at least one Interaction, and then potentially re-executing the Interaction from that invalid point. We point out some problems with using standard compensation order (as defined in the Sagas paper) when doing this type of recovery response. We then define a new type of recovery, called {\em replacement recovery}, that attempts to avoid these problems.

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