Critical Success Factors
for
system-of-system
architecture / engineering
25 October 2006
Neil Siegel
Sector Vice-President, Technology
Northrop Grumman Mission Systems
0
Copyright 2005 Northrop Grumman Corporation
SoS design basics – one person’s view
 Understand the work-flow and dynamic behavior of
the system
 “Long mission threads”
 Simultaneous operations
 Capacity
 Port-to-port timing
 Etc.
 Separate the implementation of the structure from
the implementation of the “meat”
 Exercise the structure at scale early and often
 Design for allowed / unallowed dynamic behavior
 “DC timing diagram” analogy
 Establishing boundaries and linkages
 Tight versus loose coupling
 Where to use each
A small number of abstractions (“views”) are helpful.
Science + engineering + art. Simplicity is a virtue.
1
Copyright 2005 Northrop Grumman Corporation
Fitting the work to the distribution of
skills in a real team
 Implementation can vary significantly in complexity
 In any large team, skill level across the team will vary
significantly
 Matching significantly improves the likelihood of a
desirable outcome
 Specific, tangible design steps to partition the design
into “zones of pre-determined implementation
complexity”
2
Copyright 2005 Northrop Grumman Corporation
Design for quality factors
 We are better as an industry at designing for highlyvisible factors (e.g., functionality) than for underlying
quality attributes (e.g., MTBF)
 Real-world practice seems to result in a huge
variance in achieved quality
 Probably an indication of an immature state-of-practice across
our industry
 Not clear if the underlying cause is lack of skill or
lack of focus
 A big killer of programs!
3
Copyright 2005 Northrop Grumman Corporation
Accept the limitations of our intuition
 The relationship between improvement in a technical
factor and improvement in observed system
performance is not always obvious
 Yet we all too often depend on intuition, or make use
of hidden assumptions that do the same thing
 Link technical predictors to operational predictors
4
Copyright 2005 Northrop Grumman Corporation
Integrating people into the system’s
business process
 Building successful system-of-systems is a
process that must include a business-processreengineering aspect
 Understand the sociology of your user
community, not just what they say
 Perform a careful partitioning of what the human
can do best, and what the computer can do best
 Effective and credible
 Don’t ask the human for data the computer can figure out
 Support the stressed user
 Crossing security domains
5
Copyright 2005 Northrop Grumman Corporation
Summary
 At system-of-systems scale, things sometimes scale
badly / non-intuitively
 Unplanned dynamic behavior is the source of many
of the hard problems
 Not all people are equally skilled, so designs that are
based on a tacit assumption that they are all equally
skilled are risky
 The large dynamic range of quality outcomes is a
sign of immature state-of-practice
Informing the system-of-systems design through
domain knowledge seems essential
6
Copyright 2005 Northrop Grumman Corporation