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By imposing a single hierarchy on data, XML makes queries brittle in the sense that a query might fail to produce the desired result if it is executed on the same data organized in a different hierarchy, or if the hierarchy evolves during the lifetime of an application. This paper presents a new transformation language, called XMorph, which supports more flexible querying. XMorph is a shape polymorphic language, that is, a single XMorph query can extract and transform data from differently-shaped hierarchies. The XMorph data shredder distills XML data into a graph of closest relationships, which are exploited by the query evaluation engine to produce a result in the shape specified by an XMorph query. |
