As mentioned, Ecore models consists of EPackages containing EClassifiers (EClasses and EDataTypes) containing EStructuralFeatures (EAttributes and EReferences) and EOperations, and possibly annotation with EAnnotations. This structure is stored (serialized to) files with the "ecore" extension, i.e. ending in ".ecore". Eclipse has a file creation wizard for Ecore models that lets you create such files. It will then open it in the default tree-based Ecore editor, so you can build the structure of Ecore model elements. However, there are you alternatives you should also consider, to make editing more comfortable and efficient. Below we'll describe the default editor and some of the alternatives.

The default tree-based Ecore editor