Merge as a Lattice-Join of XML Documents

We explore theoretical foundations of the Merge operation. Merge functions as a kind of “recursive union” over similarly structured XML documents to produce a new XML document, and can be used for creating aggregates over streams of XML fragments. We describe the Merge operation and show that Merge is in fact the join operation of an upper semi-lattice of conformant documents. Our work relies on a representation of unordered XML documents as sets of attributed paths. We have found this representation useful for comparing the information content of documents, and determining when a given document satisfies certain key-like constraints.

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