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Schemes of Storing XML Query Cache

XML query caching for XML database-backed Web applications began to be investigated recently. However, the issue of how the cached query results are stored has not been addressed despite its practical significance. In this paper, we deal with the schemes of storing XML query cache. A fundamental problem encountered in designing an efficient storage structure for XML query cache is that there exist performance tradeoffs between the two major types of operations on a cached query result. The two are (1) retrieving the whole of it to return the query result and (2) updating just a small portion of it for its incremental refresh against the updates done to its source. We consider eight different schemes of storing XML query cache, which are categorized into three groups: (1) the schemes based on the plain text file, (2) the schemes based on the persistent DOM (PDOM) file, and (3) a scheme employing an RDBMS. All are implemented, and performance of the two operations in each scheme was evaluated.