A Mapping Model for Transforming Nested XML Documents

XML has been extensively adopted in many modern data sharing applications. Following the relational setting, we might expect to directly use XQuery expressions to describe semantic mappings between schemas for transforming nested XML documents. Yet we observe that such an undecorated mapping representation is becoming one of the sources that complicate the ubiquitous tasks such as constructing, maintaining, and refining schema mappings. In this paper we propose a model, called mapping & correlation (Macor), to represent nested schema mappings. With Macor, a full mapping is modeled as a number of simple, partial atomic ones that are correlated with correlations. As a result, the full mapping can be modeled incrementally in a piecemeal fashion, and when refining or maintaining the mappings, Macor makes it possible to locate modifications to few atomic mappings and related correlations, and reuse other parts of the full mapping.