1. A method implemented by a computer in response to execution of program code by a processor of said computer, comprising: acquiring metadata defining a first object model including extensible entities, the first object model comprising an instance of a metaobject; acquiring metadata defining an extension object model, the extension object model to extend at least one of the extensible entities of the first object model; merging the first object model and the extension object model to create metadata defining an extended object model, the extended object model comprising an instance of the metaobject, the merging including identifying a node of the extension object model pointing to a node of the first object, adding the node to the first object model when the node of the extension object model is not an addressing node, and not adding the node to the first object model when the node of the extension object model is an addressing node; receiving a request for data associated with an instance of the first object model; and retrieving data associated with the instance of the first object model based on the metadata defining the extension object model, wherein the extension object model comprises an instance of the metaobject.