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Abstract
This document specifies Pairtree, a filesystem hierarchy for holding objects that are located within that
hierarchy by mapping identifier strings to object directory (or folder) paths two characters at a time. If
an object directory (folder) holds all the files, and nothing but the files, that comprise the object, a
"pairtree" can be imported by a system that knows nothing about the nature or structure of the
objects but can still deliver any object's files by requested identifier.
With XML becoming an ubiquitous language for data interoperability purposes in various domains, efficiently querying XML data is a critical issue. This has lead to the design of algebraic frameworks based on tree-shaped patterns akin to the tree-structured data model of XML. Tree patterns are graphic representations of queries over data trees. They are actually matched against an input data tree to answer a query.