SYSTEM ARCHITECTING – VIEWS vs.
FUNCTIONS vs. ALTERNATIVES
Dr. Howard Eisner
Professor Emeritus, GWU
SEDC CONFERENCE, April 2014
SCOPE
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1. Definition of System Architecture
2. Preferred Architecting Process
3. Clarification of Views-Functions Notions
4. How to Consider Alternative Architectures
5. Approach to Considering Both Hardware
and Software in Architecting Process
SELECTED KEY SOURCES
(from the ‘90s)
• 1. Eberhardt Rechtin – System
Architecting
• 2. C3ISR- DoDAF Framework
• 3. Rechtin and Maier – The Art of System
Architecting
• 4. Eisner – Essentials of Project and
Systems Engineering Management
VIEWS - 1
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DODAF
3 VIEWS – OPERATIONAL; SYSTEM; TECHNICAL
ESSENTIAL VIEWS
SUPPORTING VIEWS
VIEWPOINTS
DODAF SET THE STAGE FOR MANY
APPROACHES ACROSS THE GOVERNMENT
VIEWS - 2
• ARE THE VIEWS ABOUT THE PREFERRED
ARCHITECTURE?
• CAN WE INFER THE ARCHITECTURE FROM THE
VIEWS?
• EXAMPLE – HUMAN PICTURES
• DO WE HAVE A GENERALLY ACCEPTED
DEFINITION OF A SYSTEM ARCHITECTURE?
• WHERE DOES THAT LEAVE US?
FUNCTIONS
• C3ISR: COMMAND, CONTROL,
COMMUNICATION, INTELLIGENCE,…..
• USUALLY WELL-DEFINED, AND HAVE STATED
REQUIREMENTS FOR FUNCTIONS AND SUBFUNCTIONS
• FUNCTIONAL DECOMPOSITION A WELL
ACCEPTED PROCEDURE
• NO CLEAR RELATIONSHIP BETWEEN
FUNCTIONS AND VIEWS
ALTERNATIVES
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NOT A CENTRAL THEME IN DODAF
STRONG NOTION IN VARIOUS PARTS OF DoD
(I.E., AoA – Analysis of Alternatives)
A WEAKNESS IN DODAF
HOW DO WE KNOW/ASSURE THAT THE
ARCHITECTURE DEFINES A COST-EFFECTIVE
SOLUTION TO THE CUSTOMER’S PROBLEM?
ARCHITECTING A SYSTEM –
DODAF’s 6 STEPS
• “1. Determine intended use of architecture
• 2. Determine scope of architecture
• 3. Determine data required to support architecture
development
• 4. Collect, organize, correlate and store architectural
data
• 5. Conduct analyses in support of architecture
objectives
• 6. document results in accordance with decision-maker
needs”
• ?????????
KEY ROLES IN ARCHITECTING
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A. FUNCTIONS
B. ALTERNATIVES
--------------------------------------------------------THESE ARE CRITICAL TO DEVELOPING A
SYSTEM ARCHITECTURE BY SYNTHESIZING A
SET OF ALTERNATIVES
• A CHART OF ALTERNATIVE DESIGN
APPROACHES (Columns) FOR ALL FUNCTIONS
and SUB-FUNCTIONS (Rows)
KEY STEPS IN PREFERRED
ARCHITECTING PROCESS
• 1. FUNCTIONAL DECOMPOSITION AND
ALLOCATION OF REQUIREMENTS
• 2. SYNTHESIS (FORMAL DEFINITION OF
SYSTEM ALTERNATIVES)
• 3. ANALYSIS (FORMAL EVALUATION OF
ALTERNATIVES)
• 4. COST EFFECTIVENESS ASSESSMENT OF
ALTERNATIVES  PREFERRED ALTERNATIVE
SOFTWARE ARCHITECTURE NOTIONS
page 1 of 2
• GARLAN (2000): “Organization of a system as a
composition of components, global control structures,
protocols for communication, synchronization and data
access, assignment of functionality to design elements,
physical distribution, scaling and performance, and
dimensions of evolution”
• MAIER 1(2006):”The fundamental organization of a
system, embodied in its components, their relationship
to each other and the environment, and the principles
governing its design and evolution”
SOFTWARE ARCHITECTING NOTIONS
page 2 of 2
• MAIER 2: “The embodiment of a set of design
decisions that define essential characteristics
of the system”
• TAYLOR, et.al. (2010): “a set of principal design
decisions made about the system…whose key
elements that make up the basic building
blocks are (a) data elements, (b) processing
elements, and (c) connecting elements”
SYSTEM ARCHITECTING DEFINITION
• A SYSTEM ARCHITECTURE IS “AN
ORGANIZED TOP-DOWN SELECTION AND
DESCRIPTION OF DESIGN CHOICES FOR
ALL THE IMPORTANT SYSTEM
FUNCTIONS AND SUB-FUNCTIONS,
PLACED IN A CONTEXT TO ASSURE
INTEROPERABILITY AND THE
SATISFACTION OF SYSTEM
REQUIREMENTS”
CONCLUSIONS
• 1. A DEFINITIVE SYSTEM ARCHITECTING
APPROACH IS PRESENTED THAT LEADS TO A
PREFERRED ARCHITECTURE, BASED UPON
FUNCTIONS AND ALTERNATIVES
• 2. A COST-EFFECTIVE SOLUTION DOMINATES
THINKING AND ARCHITECTING PROCEDURE
• DODAF VIEWS CAN BE ADDED AFTER
ARCHITECTURE KNOWN
• SOFTWARE WELL INTEGRATED
FUTURE RESEARCH
• 1. EFFICIENT WAYS OF INTEGRATING
RECOMMENDED APPROACH AND DODAF, e.g.,
USE RECOMMENDED APPROACH TO DEVELOP
A PREFERRED SYSTEM ARCHITECTURE; THEN
PROVIDE VIEWS OF THAT ARCHITECTURE THAT
HELP TO FURTHER EXPLORE AND DEVELOP
PARTS OF THAT ARCHITECTURE
• 2. INTEGRATE SOFTWARE ARCHITECTURE INTO
THE ABOVE