The choice of sharing model (objects versus plain shared memory), memory consistency model and coherence protocol are all fundamental aspects of the design of distributed shared data systems. Unfortunately, no single sharing model, memory model or coherence protocol is suitable for all applications. In this paper, we describe the design of an extensible distributed shared data framework, called the Extensible Coherence Interface (ECI), that gives the application layer complete control over how data is shared, including whether to share data on a per-object basis or per-page, which memory model to use, and how coherence is enforced for a region of shared memory. The ECI implementation itself simply acts as a layer for transporting and dispatching distributed events among objects at the application layer.