Further Reading - Model-Driven and Software Product Line Engineering - page 228

determinate states. For instance, it is not possible to have
both the Keypad feature SELECTED , the CardReader feature
UNSELECTED and to execute a set of commands.
To transform VML specifications into a set of model
transformations in charge of transforming reference
architecture models into final products, the authors have
created a High Order Transformation (HOT). A HOT
is a model transformation that generates other model
transformations. For executing the created HOT, the authors
propose first to transform VML specifications into models
that conform to a VML metamodel . Thus, for instance, for
line 6 of the VML specification from Listing 8.1, the HOT
generates a transformation rule to transform the reference
architecture model from Figure 8.6 into a model including the
connectionbetweenthe KeypadReader and LockControlMng
components by using the IAccess interface.
Thus, when a product designer creates a feature
configuration, the generated model transformations are
executed and the final product is derived. The execution
ordering of the generated model transformations must be
predefined, and they are fixed to avoid inconsistencies in the
final product.
8.9.4. Voelter and Groher's approach
VoelterandGroher,in[VÖL07b],provideatoolchain,which
inspired our work.
Problem space: expressing variability and configuring
products . Voelter and Groher's approach proposes to create
metamodels in conjunction with cardinality-based feature
models to capture and express variability. This approach
supports the explicit and separated modeling of variability
in metamodels and feature models. Product line architects
create different metamodels during domain engineering;
each metamodel captures some concerns related to different