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refinement route is not always appropriate, but the rewards of doing so are
considerable; this is what the model-driven approach is trying to do.
Work to raise the abstraction level at which designs are formulated has
been a major research thread for a long time and, as should now be clear, was
an important influence on the development of the ODP viewpoints. However,
the ideas gained prominence in 2001 when the OMG brought much of the ear-
lier thinking together in their MDA white paper [92]. This focused initially on
one particular problem, the decoupling of application designs from the details
of the growing number of middleware platforms available. The answer pro-
posed was to capture the application detail in a quite abstract model and then
provide tools that could specialize this single design for each of the platforms
available.
One of the main contributions was to recast thinking that had previously
been in terms of translation between languages with different grammars so that
the ideas were expressed as models whose form was governed by corresponding
metamodels (although a metamodel is still, basically, just a grammar). If the
transformation that was needed from abstract and concrete models could be
defined in terms of metamodels, a single tool generated from them could be
used for transforming the whole family of models that shared the same meta-
model (see figure 15.1). In practice, transformations need to be parameterized
to make them more widely applicable, so the process is steered by a combi-
nation of the material embedded in the transformation and some additional
information supplied when a particular transformation activity is performed.
Later, the OMG extended their architecture to support more than
one refinement step, and identified three major modelling levels, yielding
abstract
model
A
language
metamodel
for A
additional
information
transformation
engine
transformation
specification
concrete
model
B
language
metamodel
for B
FIGURE 15.1: A framework for model transformations.
