Extending types hosted in database to other platforms

Aspects of the subject matter described herein relate to extending types hosted in a database to other platforms. In aspects, a database may store objects according to a one type system while an application accessing the database may store objects according to another type system. To allow the application to understand the types, a mapping mechanism may be employed that maps from the types of type system of the database to types of a type system of the application. The mapping mechanism may utilize metadata associated with the data in mapping between types. In conjunction with mapping a source type to a target type, a target object may be instantiated and populated with properties of a source object of the source type.