DO-178C

Report
DO-178C the future of Avionics Certification
Martin Beeby, European Manager, Atego HighRely
©
© 2012
2012 Atego.
Atego. All
All Rights
Rights Reserved.
Reserved.
1
What is DO-178
 RTCA DO-178: “Software Considerations in Airborne Systems and
Equipment Certification”
 Developed by Industry and Government committees
 Many compromises to satisfy different goals: “Consensus”:
•
Collective opinion or concord; general agreement or accord
[Latin, from consentire, to agree]
 Not a recipe book or “How To” guide
 Guidance not prescription
 Lawyers versus Software Engineers; who wins?
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2
DO-178: Evolution History
Doc
Year
Basis
DO-178
1980-82
498 & 2167A Artefacts, documents, traceability,
testing
DO-178A
1985
DO-178
Processes, testing, components,
four criticality levels, reviews,
waterfall methodology
DO-178B
1992
DO-178A
Integration, transition criteria,
diverse development methods,
data (not documents), tools
DO-178C
2012
+Supplements.
DO-178B
Reducing subjectivity; Address
MBD,OO, tools, Formal methods,
etc.
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Themes
3
Avionics Safety History: 1946 - 2008
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4
Safety: the precursor to DO-178
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5
Safety, System, Software & Hardware
Safety
Assessment
ARP 4761
System Development
• Architecture
ARP 4754
• Criticality Level
SW Rqmts
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HW Rqmts
Tests
Tests
Software
DO-178
Hardware
DO-254
6
Functional Safety
 The Functional Safety framework surrounding DO-178 similar to:
⁻
IEC 61508 – Industrial systems development
⁻
ISO 26262 – Automotive systems development
⁻
EN 51208 – Railway systems
⁻
IEE 7-4.3.2 – Nuclear Power Systems
 Objective based guidance gives development freedom with compromising
the use of new technology.
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7
Why change DO-178B
 Almost 20 years since DO-178B released
 Software Development landscape has changed ...
 Advancements in:
-
Tools & automation
-
Modelling & Simulation
-
Object Oriented Technology
-
Formal Methodologies
 Commercial world has embraced the above; Avionics has slowly followed
 Alternate Means of Compliance does not provide a consistent mechanism
for certification
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8
DO-178C
 Since 2005, committees have met to discuss, and update, DO-178B
 Like 178B, included Industry & Agencies
 Unlike 178B, more Tool Vendors
 Obvious focus on “acceptability” of certain types of tools, particularly
“theirs”
 Predominantly America & Europe, nearly equal; quarterly meetings
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9
DO-178C : Seven “Sub-Groups” (SG’s)
 SG1: Document Integration
 SG2: Issues & Rationale
 SG3: Tool Qualification
 SG4: Model Based Design (MBD) & Verification
 SG5: Object Oriented (OO) Technology
 SG6: Formal Methods (FM)
 SG7: Safety Related Considerations (and ground-based systems)
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10
DO-178C
 Unlike the DO-178A to DO-178B update, the “core” update to 178C is
modest
 Instead, changes are handled via four “Supplements”, which “clarify”:
-
Tools Supplement
-
MBD Supplement
-
OO Supplement
-
FM Supplement
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11
Deliverables
 DO-178C/ED-12C
Software Considerations in Airborne Systems and Equipment Certification
 DO-248C/ED-94C
Supporting Information for DO-178C and DO-278A
 DO-278A/ED-109A
Software Integrity Assurance Considerations for Communication, Navigation,
Surveillance and Air Traffic Management (CNS/ATM) Systems
 DO-330/ED-215
Software Tool Qualification Considerations
 DO-331/ED-216
Model-Based Development & Verification
 DO-332/ED-217
Object-Oriented Technology Supplement
 DO-333/ED-218
Formal Methods Supplement
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12
Software Tool Qualification Considerations (D-330)
 Tool Qualification Considerations is a stand alone document that is
consistent with and follows the structure of DO-178C
 It recognizes that tools occupy their own domain
⁻
They are not airborne software
⁻
Tool qualification can apply to hardware and ground-based systems also
 DO-330 is a stand-alone approach to tool qualification that could be called
out by any standard
⁻
Domain Specific Guidance in the calling document
⁻
Tool qualification guidance from DO-330 based on crteria defined in the
domain specific guidance
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13
Same Basic Tool Qualification Principles
 The tool qualification is unchanged from DO-178B:
⁻
The purpose of the tool qualification process is to ensure that the tool
provides confidence equivalent to that of the process(es) eliminated, reduced,
or automated
⁻
The higher the risk of a tool error adversely affecting system safety, the higher
the rigor required for tool qualification
 Determining if tool qualification is needed, or unchanged from DO-178B:
⁻
“…when processes of this document are eliminated, reduced, or automated
by the use of a software tool without its output being verified as specified…”
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14
DO-178C Tool Qualification Levels
 DO-178B Development and Verification Tools terminology is no longer
used. DO-178B Definitions:
⁻
Development Tools: whose output is part of airborne software and thus can
introduce errors
⁻
Verification Tools: that cannot introduce errors but may fail to detect them
 DO-178C identifies 5 Tool Qualification Levels (TQL1-5) based on 3 criteria
(see next slide):
⁻
For criteria 1 and 3, the basic concept and required objectives are similar to
that applied under DO-178B
⁻
New criterion 2 introduced to provide increased objectives for certain tool
usage scenarios
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15
Advantages of Model-Based Development (DO-331)
 Early animation of requirements
 Shared language between systems and software engineers
 Increased responsiveness to requirements changes
 Ability to use autocode and simulation as a means of verification
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16
Model Based Development Supplement (DO-332)
 Provides additional guidance for Model Based Development Technology
and Related Techniques
 The MBD Supplement provides a set of approaches that can encompass
most organisations uses of MBD
⁻
A Framework for using MBD is established
⁻
Guidance on where certification credit for model simulation is provided
⁻
Core techniques of DO-178C are maintained in MBD
⁻
⁻
⁻
⁻
Requirement Levels
Requirement Based Testing
Traceability
Structural Coverage
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17
Object-Oriented Supplement (DO-332)
 Provides additional guidance for Object-Oriented Technology and Related
Techniques
 Much of the DO-178C OOT Supplement is devoted to establishing core
terminology, background and interpretation
⁻
Few additional objectives or activities are identified
 Additional OOT objectives:
⁻
Verify local type consistency
⁻
Verify the use of dynamic memory management is robust
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18
Criteria for choosing whether to use OOT
 Project technical criteria:
⁻
Potential benefit from increased expressive power in design/code –
encapsulations, class hierarchies and polymorphism
⁻
Nothing new here… these were original drivers behind OOT
 Environmental criteria:
⁻
Guidance, Human Resources, Tools
⁻
In industry these are all currently available…
 Summary:
⁻
OOT is a viable technique if the software design would benefit from its
expressiveness
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19
Formal Methods Supplement (DO-333)
 DO-178B allowed for consideration of formal methods as an alternate
method “to improve the specification and verification of software”
 Included a set criteria to determine the requirements to which formal
methods could be applied
⁻
Safety related
⁻
Definable by discrete mathematics
⁻
⁻
⁻
⁻
⁻
Involved complex behavior
Concurrency
Distributed processing
Redundancy management
Synchronization
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20
Formal Methods Supplement
 The formal methods supplement applies where formal methods analysis is
replacing testing evidence in the submission
 There is no intent to suggest that formal methods adoption is an “all in”
decision
⁻
Can be a selective adoption/migration for subsets of the system
 The supplement mimics the core DO-178 document structure
 Does not preclude traditional software testing even when comprehensive
formal methods are applied
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21
DO-178C Supplements Summary: Changing the Level of Abstraction
 There is an underlying synergy between the new DO-178C documents and
supplements:
⁻
Object Oriented Technology (OOT), Model Based Design and Verification
(MBDV), Tools, Formal Methods
 All are moving in a common direction:
⁻
Still enforce the objectives of DO-178C
⁻
Enable systematic verification and/or increased level of abstraction
⁻
Enabling more powerful development techniques to tackle the issues of
increased complexity and limited resources
 Fundamental approach of DO-178 remains intact
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22
DO-178C: The Future
 DO-178C will be mandated by EASA, FAA, and others at some time in the
future.
⁻
When?
⁻
But it will be mandated!
 The model of providing Technology Supplements will be applied to future
standards
⁻
Maintain a core approach
⁻
Enable approaches for new technologies to be added
⁻
Be able to react more quickly by just adding supplements
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23
DO-178C: The Future
 How will DO-178C affect systems development?
 How did DO-178B affect systems development?
⁻
No specific life-cycle model required
⁻
Say what you are going to do
⁻
Do it
⁻
Show the evidence you did it
 Analogous to ISO 9001, or CMMI
Good Engineering Practice
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24
SEI CMMI Maturity Levels
Level 1
 SEI CMMI’s 5 Levels:
Level 2
⁻
Initial
Level 3
⁻
Repeatable (disciplined)
Level 4
⁻
Defined (consistent))
Level 5
⁻
Managed (predictable)
⁻
Optimizing (continuous improvement)
 Each level is a perfect superset of the
preceding level
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25
Perfection
DO-178 Quality/Cost
100 % Perfection
Robust. Testing
Functional Testing
Unit Testing
Code Reviews
26
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Detailed Rqmts
Plans & Processes
CO$T
DO-178C: The Future
 By Enabling new technologies it is possible to reduce the cost of
development
⁻
Reduced Time of Development
⁻
Ability to increase system capabilities
⁻
Reduce Obsolescence
 Fundamental Safety approach is not compromised
⁻
Functional Safety Framework remains
⁻
Core approaches of DO-178 remain
⁻
New technologies have to fit within this framework
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