Eclipse OCL is used as a component in a variety of other Eclipse projects such as Acceleo, BIRT, GMF, Modisco, QVTo.
The evolution from the mature to the UML-aligned models provides a choice between the mature APIs that offer limited forward functionality, and the experimental new APIs that will be promoted to non-experimental form in the Juno release.
The new code already offers a fully modeled Standard Library that can be extended or replaced. The new OCL grammars are extended internally from Essential OCL to OCLinEcore or Complete OCL, but the associated Concrete Syntax to Abstract Syntax is not yet model-driven and so awkward to extend.
Full extensibility is planned for the Juno release with QVT Core and Relational editors demonstrating that extensibility.