Document stores

Sparked by the explosive growth of web content and applications, probably one of the most well-known and most used types of NoSQL databases are in the document category. The key concept in a document store, as the name suggests, is that of a semi-structured unit of information often referred to as a document. This can be an XML, JSON, YAML, OpenOffice, or, MS Office, or whatever other kind of document that you may want to use, which can simply be stored and retrieved in a schema-less fashion. Examples of Document stores include the wildly popular MongoDB, Apache CouchDB, MarkLogic, and Virtuoso: