This white paper explains the benefits of the Model-Based Design
(MBD) approach and Object-Oriented Technology (OOT) that DO-178C
provides. It also specifically focuses on the usage of Models and
COTS Qualifiable tools that automate or facilitate the verification
and validation of avionics applications constructed from Models in
order to ensure that there is no unintended function.
Software running in Aircraft cockpits has dramatically increased
in complexity since DO-178B's revision in 1992. Furthermore,
over the past 20 years, software development methods have made
significant leaps forward and DO-178B has begun to show its age
with respect to the new technology introduced to facilitate
software development.
This year the newly revamped DO-178C standard sets the
certification process record straight by embracing modern
technology. DO-178C does not only solidify its foundation by
clarifying its core document but also builds the infrastructure to
support modern software development techniques already commonly
used in avionics development for at least a decade. Fortunately,
DO-178C upgrades and clarifies DO-178B. DO-178C therefore considers
four techniques of contemporary software development practices
which are published as supplements to the core document: 1.
Software Tool Qualification Considerations (TQC) [DO-330]. 2.
Model-Based Design and Verification Supplement (MBDV) [DO-331]. 3.
Object-Oriented Technology Supplement (OOT) [DO-332]. 4. Formal
Methods Supplement (FM) [DO-333].
Organizations can see gains not only in the reduction of the
development cycle but also in the overall improvement of the
DO-178C certification process; including reduction of schedule and
costs, and improvements in the quality and reliability.
In the old school of thought, the methodology relies on textual
specifications and physical prototypes. That is why the informal
Text-Based Design approach is tightly associated with the waterfall
methodology where all the textual requirements are manually coded,
inspected, and tested on a real embedded system. In this method,
changes in any part of the waterfall chain are very costly and
time-consuming, leaving almost no room to iterate on the
design.
By contrast, in the Model-Based Design approach, the
specifications are self-contained in the Human Machine Interface
(HMI) Model. The HMI requirements are defined in an unambiguous way
and often captured in a formal definition language. Model-Based
Design offers a collaborative approach to avionics development and
allows engineers to inexpensively experiment with various concepts
by deferring hardware integration until much later in the
development process. Correcting problems in the early modeling
phase is undeniably the strongest argument in favor of the
Model-Based Design approach for developing certifiable or
non-certifiable avionics applications.
This white paper is based on "MBD & Code Generation: A
Cost-Effective Way to Speed up HMI Certification," by Luc
Marcil, Presagis, Montréal, Québec (Canada) which was presented at
the 30th Digital Avionics Systems Conference in October 18th, 2011.
© 2011 IEEE.