Current information systems are grounded on the exploitation of data coming from an increasing number of heterogeneous sources. Coping with the variety of data requires paradigms for effectively accessing and querying information that adapt to the different types of sources, as well as declarative high-level languages to drive the data processing and data quality tasks. The BOREAL team focuses on the study of foundational and applied issues of reasoning, in a context of data variety. The team builds upon its expertise in knowledge representation and automated reasoning to devise novel techniques for heterogeneous and federated data management which leverage in particular on expressive rule languages.