In accordance with an embodiment, described herein is a system and method for providing extensibility in an analytic applications environment, including a semantic layer that enables the use of custom semantic extensions to extend a semantic data model (semantic model). In accordance with an embodiment, customizations to the out-of-the-box semantic model are performed using a layered approach, wherein the factory code for the semantic model remains intact, with changes/delta editable by the customer layered on top of that model, such that the changes can be patched/reversed if necessary.