Representing and Querying Changes in Semistructured Data

Abstract

Semistructured data may be irregular and incomplete and does not necessarily conform to a fixed schema. As with structured data, it is often desirable to maintain a history of changes to data, and to query over both the data and the changes. Representing and querying changes in semistructured data is more diffcult than in structured data due to the irregularity and lack of schema. We present a model for representing changes in semistructured data and a language for querying over these changes. We discuss implementation strategies for our model and query language. We also describe the design and implementation of a "query subscription service" that permits standing queries over changes in semistructured information sources.