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The expert pattern is the most often used refinement rule in OO design. One
feature of this rule is that it does not introduce more couplings by associations
between classes into the class structure. It also ensures that functional responsi-
bilities are allocated to the appropriate objects that
knows
the data needed for
the responsibilities assigned to them.
Encapsulation.
The
encapsulation rule
says that if an attribute of a class
C
is
only referred directly in the specification (or code) of methods in
C
, this attribute
canbemadea
private attribute
;anditcanbemade
protected
if it is only directly
referred in specifications of methods of
C
and its subclasses.
Class Decomposition.
During an OO design, we often need to decompose a
class into a number of classes. For example, consider classes
C
1
::
D a
1
,
C
2
::
D a
2
,
and
D
::
T
1
x, T
2
y
. If methods of
C
1
only call a method
D
::
m
()
{...}
that only in-
volves
x
,andmethodsof
C
2
only call a method
D
::
n
()
{...}
that only involves
y
,we
can decompose
D
into two
D
1
::
T
1
x
;
m
()
{...}
and
D
2
::
T
2
y
;
n
()
{...}
, and change
thetypeof
a
1
in
C
1
to
D
1
and the type of
a
2
in
C
2
to
D
2
. There are other rules for
class decomposition in [14].
An important point here is that the expert pattern and the rule of encap-
sulation can be implemented by automated model transformations. In general,
transformations for structure refinement can be aided by transformations in
which changes are made on the structure model, such as the class diagram, with
a diagram editing tool and then automatic transformation can be derived for
the change in the specification of the functionality and object interactions. For
details, please see our work in [23].
3
Integrating rCOS Support into Model-Driven
Development Process
In a realistic project there are more
activities
than just design. These activi-
ties are performed by project team members in different
roles
,suchas
Admin-
istrator, Analysis Modeler, Architecture Modeler, Design Modeler, Construction
Manager, Construction Programmer, Model Manager
,and
Version Manager
[31].
The concepts of activities and roles define at which point various models, that are
also informally called
artifacts
, are produced by which roles, and what different
analysis, manipulation, checking and verification are performed, with different
tools. The concept of roles is also useful for the control of the work flow in that
different roles are allowed to access and modify certain models in the devel-
opment environment. These concepts and ideas have been implemented in the
industrial tool, MasterCraft, for model transformation [31]. In this section, we
use the our experience with the in the recent work on the Common Compo-
nent Modelling Example (CoCoME) to show how the rCOS methodology can
be integrated into a model-driven development processes in supporting the de-
velopment activities. We first introduce the modelling example, that is followed
by a summary of the application of rCOS.
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