XQuery processing over NoSQL stores

Using NoSQL stores as storage layer for the execution of declarative query processing using XQuery provides a highlevel interface to process data in an optimized manner. The term NoSQL refers to a plethora of new stores which essentially trades off well-known ACID properties for higher availability or scalability, using techniques such as eventual consistency, horizontal scalability, efficient replication, and schema-less data models. This work proposes a mapping from the data model of different kinds of NoSQL stores— key/value, columnar, and document-oriented—to the XDM data model, thus allowing for standardization and querying NoSQL data using higher-level languages, such as XQuery. This work also explores several optimization scenarios to improve performance on top of these stores. Besides, we also add updating semantics to XQuery by introducing simple CRUD-enabling functionalities. Finally, this work analyzes the performance of the system in several scenarios.