MayBMS: A Probabilistic Database Management System Christoph Koch, Cornell University Databases that contain uncertain data arise naturally in many data management scenarios, such as Web information extraction, data cleaning, data integration, sensor data management, and scientific databases. There are currently no scalable systems for managing and querying such databases. In this talk I present MayBMS, a database management system for efficiently managing and processing large collections of uncertain data that is currently under development at Cornell. MayBMS is based on a clean yet expressive query language that captures many important use cases of probabilistic databases, including what-if queries and the conditioning of databases using new evidence. MayBMS employs a carefully designed succinct representation system for probabilistic databases called U-relations, which nicely unifies various approaches to representing uncertain data, such as c-tables, relational, in particular vertical, decomposition, and probabilistic graphical models. U-relations allow for the natural reuse of mature relational storage, indexing and query processing techniques to build scalable probabilistic database systems. In addition to the exact processing of probabilistic database queries on U-relations, I discuss the efficient approximation of expressive, compositional queries on probabilistic databases.