document: XML design for relational storage Design principles for XML schemas that eliminate redundancies and avoid update anomalies have been studied recently . Several normal forms , generalizing those for relational databases , have been proposed . All of them , however , are based on the assumption of anative XML storage , while in practice most of XML data is stored inrelational databases . In this paper we study XML design and normalization for relational storage of XML documents . To be able to relate and compare XML and relational designs , we use an information-theoretic framework that measures information content in relations and documents , with higher values corresponding to lower levels of redundancy . We show that most common relational storage schemes preserve the notion of being well-designed ( i.e. , anomalies - and redundancy-free ) . Thus , existing XML normal forms guarantee well-designed relational storagesas well . We further show that if this perfect option is not achievable , then a slight restriction on XML constraints guarantees a `` second-best '' relational design , according to possible values of the information-theoretic measure . We finally consider an edge-based relational representation of XML documents , and show that while it has similar information-theoretic properties with other relational representations , it can behave significantly worse in terms of enforcing integrity constraints .
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