On the integration of autonomous data marts

We address the problem of integrating a federation of dimensional data marts. This problem arises when, e.g., a large organization (or a federation thereof) needs to combine independently developed data warehouses. We show that this problem can be tackled in a systematic way because of two main reasons. First, data marts are structured in a rather uniform way, along dimensions and facts. Second, data quality in data marts is usually higher than in generic databases, since they are obtained by reconciling several data sources. Our scenario of reference is a federation (i.e., a logical integration) of various data marts, which we need to query in a unified way, that is, by means of drill-across operations. We propose a novel notion of dimension compatibility and characterize its general property. We then show the significance of dimension compatibility in performing drill-across queries over autonomous data marts. We also discuss general strategies for the integration of data marts.