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risk of misinterpreting the standard's content or following an incorrect or in-
complete sequence of development activities. This threat is further increased
by interdisciplinary issues in developing safety critical systems: in order to
avoid misunderstandings between different disciplines involved in the devel-
opment, a universally comprehensible representation of system and process
requirements - on a common and generic basis - is essential. In the context
of ISO 26262, process requirements in particular are important, as most of
the requirements from the standard are process related. A formally sound
specification of process requirements based on a well-defined terminology is
crucial for supporting a precise presentation of requirements. Furthermore,
through the formal base, process requirements and associated activities be-
come computer-readable, and some analysis steps (e.g. checking consistency)
can be automated. Especially in the context of certification, traceability be-
tween process and system artifacts is of high importance.
1.1
Design of Safety Critical Automotive Systems
The Virtual Institute DeSCAS (Design of Safety Critical Automotive Sys-
tems), which is funded by the Helmholtz Association, strives for defining a
process framework and related methods to support interdisciplinary develop-
ment of safety critical assistance and automation systems in the automotive
domain. The process framework builds on generic as well as domain depen-
dent concepts to interweave different interdisciplinary development activities.
This includes the formalization of relevant standards (e.g. ISO 26262) in or-
der to allow the automation of certain analysis methods (e.g. hazard analysis
and risk assessment) and the derivation of requirements, which may vary due
to variations in safety level classification.
1.2
Structure of the Paper
This paper will outline how the use of a standard can be improved by for-
malizing its structure. This comprises OWL (Web Ontology Language) based
formalization of the risk analysis from ISO 26262, which is applied to an
example application (lane departure warning system). Since safety require-
ments and associated methods as well as process phases have been modeled
in OWL, the result of the risk analysis is furthermore used to infer concrete
requirements for a system under development. These requirements and their
dependencies are utilized to derive a safety related workflow. The different
steps of analysis and formal reasoning have been integrated in a prototype
toolchain, which especially operates on safety requirements from ISO 26262.
This paper gives a summary of the DeSCAS process framework concerning
implementation aspects and insights gained from the prototype implementa-
tion (proof of concept). This especially concerns the performance of formal
reasoning on OWL ontologies.
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