Recursive Levels Driver
Ricardo Valerdi
March 17, 2008
5. Number of recursive levels of design
• Central question: How can the integration complexity of
subsystems one layer below the system-of-interest be
operationalized?
• Hypothesis: The integration complexity of subsystems is
a predictor of systems engineering effort.
• POC: John Rieff
• References
– Marksteiner, B., “Recursive Levels and COSYSMO”, October
2007. (working paper)
# of recursive levels in the design
The number of levels of design related to the system-of-interest (as defined
by ISO/IEC 15288) and the amount of required SE effort for each level.
0.76
0.87
1.00
1.21
1.47
Viewpoint
Very Low
Low
Nominal
High
Very High
Number of
levels
1
2
3-5
6-7
>7
More complex
interdependencies
coordination, and
tradeoff analysis
Very complex
interdependencie
s coordination,
and tradeoff
analysis
Extremely complex
interdependencies
coordination, and
tradeoff analysis
Required
SE effort
Focused on
single product
Some vertical and
horizontal
coordination
Effort multiplier ratio (EMR) = 1.47/0.76 = 1.93
Recursive
–adjective
1.pertaining to or using a rule or procedure
that can be applied repeatedly.
2.Mathematics, Computers. pertaining to or
using the mathematical process of
recursion: a recursive function; a recursive
procedure.
Possible Interpretation of “Number of Levels”
•
•
•
•
•
The largest number of decomposition levels in any branch of the system’s
specification tree
The average number of decomposition levels in the branches of the system’s
specification tree
The smallest number of decomposition levels in any branch of the system’s
specification tree
The number of levels of the system’s Work Breakdown Structure (WBS)
The number of levels on the system’s Bill of Materials (BOM)
Perhaps more importantly, interpretations of COSYSMO’s output has included
some very different variations:
a)
An estimate of all of the system engineering (i.e., requirements generation,
integration, verification, etc.) for every level of decomposition of the system
b)
An estimate of the system engineering at the system of interest level only
c)
An estimate of the system engineering at the system of interest and one level
below the system of interest
Scope
Included Effort
• Applies only to the system level and the first level of
decomposition below the top-level system where systems
engineering is being estimated
• Includes the system engineering effort necessary to support
these products and components far down on the specification
tree, such as schedule coordination and requirements
negotiation
Excluded effort
• Does not include writing all of the specifications all the way
down the specification tree
• Does not include the integration and verification of products
and components far down on the specification tree