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skills has to be learned.
Figure 3 shows the basis for defining
the mapping from PIMs (expressed in
xUML) to their platform specific implementation.
“Ordinary” analyst models
(level 1) are used to populate the metamodel
of xUML (level 2), which has all the
necessary processing defined (remember
it is an executable model in its own right)
to populate a model of the implementation
(level 3). This final model, which again is
expressed in xUML, is executed to produce
the implementation. The analyst models
(level 1) are augmented with tags that act
like “compiler directives” to the translation
system and allow such facts as limited
instance populations to be exploited in
order to produce efficient target code.
Tool Support:
There are two main areas where tool
support is vital in order to reap the full
benefits of the MDA process. First, iUML
is used to provide the modeling and
SUCCESS STORY: MDA
Lockheed Martin
Application
Software
Application Software Interface
Software
Execution
Platform
Hardware
FIGURE 1:
Mission Software Main
Architectural Elements
Figure 1 shows the basis for the F-16 Mission
Software architecture; it depicts the main
architectural elements:
• Software that is unique to the application(s)
for which the embedded computer exists, it
represents some 80-90% of the total software
(in terms of long-term development cost);
• Application Software Interface, the boundary
between the Application Software and the
Software Execution Platform. This provides
the methods by which the Application Software
can make requests and use the services
of the Software Execution Platform and the
Software Execution Platform can provide its
services to the Application Software;
• Software Execution Platform, low-level
software, the purpose of which is to allow
the Application Software to run on the
hardware; The software execution platform
incorporates device drivers, the built-in test
and the RTOS;
• Hardware, the embedded system hardware
for the F-16 Mission Management system.
3
simulation environment for the xUML
models. This tool provides dedicated
intelligent support for xUML and allows
models to be simulated on host and
“debugged” visually at the UML level of
abstraction. The second part of the toolchain
is the translation environment (level
2 in Figure 3 above) where application
models are extracted from the iUML database
and used to populate the translation
engine. The translation engine is a specialization
of the intelligent Configurable
Code Generator (iCCG). iCCG allows
developers to capture their mapping
rules as xUML models and so produce
any target implementation of which they
can conceive. The specification of a
mapping from PIM to PSM in eXecutable
UML is itself highly reusable, allowing any
set of application models to be generated
onto the target.
Further details of these and other
products that support xMDA may be
obtained at www.kc.com.
Benefits:
The use of MDA with executable UML
(xMDA) has provided many benefits to
the F-16 project:
• The application models are expressed
in a completely platform independent
way and so can be reused across multiple
hardware and software platforms;
• UML modelers are isolated from the
software and hardware details and so
can concentrate on a thorough exploration
of the problem space;
• The hardware and software platforms
can be upgraded without impacting
the application models;
• Models can be tested at the earliest
opportunity by executing them in the
iUML Simulation environment;
• Rework is reduced with validated models;
• The mapping from PIM to PSM is specified
in xUML with iCCG and is highly
reusable;
• Code generation eliminates manual
coding and eliminates the defects
traditionally introduced in the coding
phase;
• The xUML models are the primary
source. Code is not maintained.
Taken altogether these MDA benefits
have reduced application development
time by 20% on the F-16 MMC program
in addition to helping them achieve complete
cross-platform compatibility. n
Acknowledgments
This article was based upon a presentation
prepared by:
Lauren E. Clark
Chief Engineer
F-16 Modular Mission Computer Software
Terry Ruthruff
Staff Specialist
　
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