Multi-model database

Most database management systems are organized around a single data model that determines how data can be organized, stored, and manipulated. In contrast, a multi-model database is designed to support multiple data models against a single, integrated backend. Document, graph, relational, and key-value models are examples of data models that may be supported by a multi-model database.

The relational data model became popular after its publication by Edgar F. Codd in 1970. Due to increasing requirements for horizontal scalability and fault tolerance, noSQL databases became prominent after 2009. NoSQL databases use a variety of data models, with document, graph, and key-value models being popular.

A Multi-model database is a database that can store, index and query data in more than one model. For some time, databases have primarily supported only one model, such as: relational database, document-oriented database, graph database or triplestore. A database that combines many of these is multi-model.

For some time, it was all but forgotten (or considered irrelevant) that there were any other database models besides Relational. The Relational model and notion of third normal form were the de facto standard for all data storage. However, prior to the dominance of Relational data modeling from about 1980 to 2005 the hierarchical database model was commonly used, and since 2000 or 2010, many NoSQL models that are non-relational including Documents, triples, key-value stores and graphs are popular. Arguably, geospatial data, temporal data and text data are also separate models, though indexed, queryable text data is generally termed a "search engine" rather than a database.

...
Wikipedia