Many NoSQL data stores have the advantage of being schema-free (although the data still has an implicit structure). However, NoSQL stores don't have convenient schema management tools for when the schema evolves with the application. This recent paper [pdf] declares and outlines a NoSQL schema evolution language for use in the admin console.
Using our evolution language, developers can specify common operations, such as adding, deleting, or re-naming properties in batch. Moreover, properties can be moved or copied, since data duplication and denormalization are fundamental in NoSQL data stores. We emphasize that we do not mean to enforce a relational schema onto NoSQL data stores. Rather, we want to ease the pain of schema evolution for application developers.
-- Stefanie Scherzinger, Meike Klettke, Uta Storl
The authors of the paper also say that that this language can be implemented by a large class of NoSQL databases.