Aggregation and Accumulation of XML Data

XML is rapidly becoming a standard for data exchange on the Internet. While XML’s document management roots have led many to focus on querying and processing of large documents, we believe much XML data will be in the form of streams. One can envision streams of XML data flowing throughout the Internet: a stream of stock quotes or minute-by-minute updates on positions of a fleet of vehicles one XML fragment per vehicle report. In this paper, we propose a new operation, Merge, which provides the capability to create aggregates over streams of data and the ability to take XML documents from different inputs and piece them together to create a new XML document. The Merge operation effectively handles highly-nested, semi-structured data and was designed to be used in an environment where there are long-running queries and stream-based data sources. We describe a flexible mechanism, called a Merge Template, which we have developed to specify how to merge two XML documents.