document: Mapping-driven XML transformation Clio is an existing schema-mapping tool that provides user-friendly means to manage and facilitate the complex task of transformation and integration of heterogeneous data such as XML over the Web or in XML databases . By means of mappings from source to target schemas , Clio can help users conveniently establish the precise semantics of data transformation and integration . In this paper we study the problem of how to efficiently implement such data transformation ( i.e. , generating target data from the source data based on schema mappings ) . We present a three-phase framework for high-performance XML-to-XML transformation based on schema mappings , and discuss methodologies and algorithms for implementing these phases . In particular , we elaborate on novel techniques such as streamed extraction of mapped source values and scalable disk-based merging of overlapping data ( including duplicate elimination ) . We compare our transformation framework with alternative methods such as using XQuery or SQL\/XML provided by current commercial databases . The results demonstrate that the three-phase framework ( although as simple as it is ) is highly scalable and outperforms the alternative methods by orders of magnitude .
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