Intro

Eclipe Modeling Framework (EMF) is a modeling framework and code generation facility for building tools and other applications based on a structured data model.
From a model specification described in XMI, EMF provides tools and runtime support to produce a set of Java classes for the model, along with a set of adapter classes that enable viewing and command-based editing of the model, and a basic editor.
The most important benefit of EMF, as with modeling in general is the boost in productivity that results from automatic code generation. [pp 23. 2.4 Generating Code Eclipse EMF.]
A domain model represents that data we want to work with. The data should be modeled irrespective of the application logic.
Eclipse EMF is used to model these domain models.EMF makes a distinction between Meta models and actual model. The meta model describes the structure of the model and the model with data is an instance of this meta model.
In the UML world, this is equivalent to a class diagram which describes the meta-model and an object digram describes the actual model.
EMF provides a pluggable framework to store the model definition, the default method is to use XMI.
The Meta model can be specified in different ways - XMI, Java annotations, UML/XML schema, textual syntax called EMFatic, Graphical editors within EMF.

EMF Metamodels

The Ecore metamodel contains the information about the defined classes.
The Ecore model allows the definition of the following elements:
- EClass
- EAttribute
- EReference: One end of an association between two classes.
- EDataType: Type of an attribute.
Ecore model editor shows the model itself as the root, followed by the packages, then classes and then attributes.
UML2 modeling is an EMF-based implementation of the UML 2.x metamodel for the Eclipse platform.

The Genmodel contains additional information for generating code, e.g. the path and file information. The genmodel contains also the control parameter how the coding should be generated.
Where to place generated code, what prefix to use for generated factory and package class names - the kind of information that is not stored in the Ecore model, but is user settable. The EMF code generator uses a generator model to store this information. Like Ecore, the generator model is itself an EMF model.
The genmodel provides all the data required for code generation by wrapping the Ecore model.

Every generated EMF class is a notifier, it can send notification whenever an attribute or reference is changed. This allows EMF objects to be observed.
Notification observers/listeners in EMF are called adapters, because they're used to extend the behaviour of the object they are attached to.
The ability to persist and reference other persisted objects, is one of the most important benefits of EMF modeling.