Formalism used

Structured

Semi-structured

Graph based

Hierarchical model

IMS, INES, Caché

LDAP, Windows registry, Caché

Document-oriented

XML: CosmosDB, SQL Server, Oracle, BaseX, MarkLogic

JSON: Dynamo, CosmosDB, MongoDB, CouchDB, PostgreSQL,  Spark

Network model

IDS, Raima DB, Cronos

Object-oriented

GemStone, Versant, DB4O

Graph

Oracle, SQL Server

Neo4j

RDF

Oracle

Set-oriented

Relational

DB2, Oracle, SQL Server, PostgreSQL, MySQL

Excel, Calc

Multidimensional

SQL Server (MDX), Cognos, SAS

Caché

Key-object

KeySQL

Map based

Key-value

Redis, Couchbase, InfinityDB, RocksDB, Tarantool,

Windows INI files

EAV/CR

TrialDB, Magento

Column store

HBase, Cassandra, Riak