An Entropy-Based Characterization of the Heterogeneity of XML Collections

The concept of heterogeneity is very important in XML data management, since many common applications must deal with large and complex collections which do not conform to a schema. Heterogeneity in XML collections can be present at many different levels (textual and structural) and needs to be addressed from several perspectives. This paper contributes a formal characterization of heterogeneity in XML collections based on information-theoretic considerations. We show how it can be applied in some important use cases, and we demonstrate its effectiveness by using it to analyze a number of relevant XML collections and retrieval approaches found in the literature. We show that a large space of highly heterogeneous collections has not been adequately addressed by these approaches.