3. The system of claim 1 , wherein the memory further stores instructions that, when executed by the at least one processor, cause the system to: receive a subtype from the user for the first entity type and a natural language description for the subtype; generate an entity in the data graph that represents the subtype; parse the natural language description to determine criteria for the subtype; and determine that first entities meeting the criteria are members of an extension of the subtype.
3. The system of claim 1 , wherein the memory further stores instructions that, when executed by the at least one processor, cause the system to: receive a subtype from the user for the first entity type and a natural language description for the subtype; generate an entity in the data graph that represents the subtype; parse the natural language description to determine criteria for the subtype; and determine that first entities meeting the criteria are members of an extension of the subtype. 4. The system of claim 3 , wherein the criteria specifies a property, a relationship and an object entity, or at least two properties and a logical operator.