Veracity is one of the so-called 4 V's of Big Data (the others being Volume, Velocity and Variety), and concerns the problem of dealing with data that might be uncertain or imprecise. This usually arises after integrating our data from different sources. One of the main challenges in this context, is to integrate all this data in such a way that insights and higher level knowledge can be extracted. Ontology-Based Data Access (OBDA) is a prominent paradigm for querying heterogeneous data sources which uses ontologies to expose data by abstracting away the details of the underlying sources. The course will provide an introduction to OBDA, in particular, the theoretical foundations on how to reason over multiple data sources by means of different ontology languages (e.g., Description Logics and Existential Rules), and how query answering can be made efficient.
