Abstract
The CloudMdsQL (Cloud Multi-datastore Query Language) polystore transformsqueries expressed in a common SQL-like query language into an optimized query execution plan tobe executed over multiple cloud data stores (SQL, NoSQL, HDFS, etc.) through a query engine. The compiler/optimizer is implemented in C++ and uses the Boost.Spirit framework for parsing context-free grammars.CloudMdsQL has been validated on relational, document and graph data stores in the context of theCoherentPaaS European project.