Model-Driven Engineering - Model-Driven and Software Product Line Engineering - page 65

- constraints specify the well-formedness rules that govern
valid domain models. MOF provides several features for
metamodel composition, extension, and re-use, including
Class inheritance ,

Package inheritance ,

Class

importation , and Package importation .

Aspartofourwork,wehaveusedEcoreasmeta-metamodel.
Ecore is a core subset of the MOF meta-metamodel where
concepts are prefixed by the letter “E”. Figure 3.12 presents a
part of the Ecore metamodel. As with MOF, EClass instances
are types. Metaconcepts that conform to EClass have identity,
state, and behavior. The state of an EClass metaconcept is
expressed by its EAttributes and EReferences . Ecore and
the Eclipse Modeling Framework (EMF) [BUD 03], which is
a framework that aims to follow the MOF standard and uses
Ecoreasmeta-metamodel,areexplainedindetailinsection3.5.

3.2.2. The nature of models

An intrinsic characteristic of MDE is the separation of
concerns of a software system into different models. In MDE,
it is possible to create and process several models from the
same system simultaneously, describing different perspectives
or points of view of different stakeholders.

The models describing a system can be classified in terms
of their level of abstraction . The level of abstraction of a
model refers to the extent of implementation details that the
model has. In other words, it indicates how close the model
is to the problem space; the closer to the problem space, the
higher the level of abstraction; the closer to the solution space,
the lower the level of abstraction. For example, stakeholders
may create high-level abstraction models that include only
domain-specific application details or only concepts regarding
the problem. Other stakeholders may create or interact
with models including details of software design. These
models can be considered as medium-level abstraction models.