# Creating Metamodel Bindings

The Eclipse OCL component provides a generic specification of the OCL Abstract Syntax Model plus bindings for two popular Eclipse metamodels: Ecore and UML. Users of the OCL API can likewise create bindings for their metamodels, to integrate OCL with their modeling languages.

The `Environment` interface has a generic type signature with several parameters, representing the metamodeling constructs required by OCL, that it borrows from UML, EMOF, and the other metamodels that it targets. The Javadoc for that interface defines the mappings, and the same type parameter names are used consistently throughout the OCL API.

To provide a metamodel binding, a client must provide implementations of the following interfaces:

- `Environment` and `EnvironmentFactory`, supplying suitable substitutions for the generic type parameters. Note that not all of these are actually required; for example, Ecore does not have the concept of `State`, so it just substitutes `EObject`

- `EvaluationEnvironment` for accessing properties of run-time instances of models

- `UMLReflection` for introspecting models (instances of thetarget metamodel)

- `OCLStandardLibrary`, providing the instances of the metamodel’s `Classifier` metaclass that implement the OCL Standard Library types

- `OCLFactory`, providing a factory for all of the metaclasses of the Abstract Syntax Model

This last item, above, necessitates furthermore that the metamodel binding provide a concrete specialization of the Abstract Syntax Model (in its entirety) that mixes in the target metamodel’s correspondents of the UML `Classifier` and `TypedElement` metaclasses. The former is required to provide compatibility of the metaclasses in the OCL `Types` with the target metamodel’s type system. The latter is required for compatibility of the metaclasses in the OCL `Expressions` package with the target metamodel’s typed elements.

### The OCL Abstract Syntax Model

The following diagram summarizes the metaclasses of the OCL `Types` package:

The following diagram summarizes the call expression metaclasses of the OCL `Expressions` package:

The following diagram summarizes the literal expression metaclasses of the OCL `Expressions` package:

The following diagram summarizes the remaining metaclasses of the OCL `Expressions` package: