Functional analysis defines the system's functions first based on user needs before considering physical implementation. It involves defining the system's modes of operation and allocating functions to each mode. An enhanced function flow block diagram (EFFBD) maps the functional flow and interfaces. System architecture then decomposes the system into physical modules and components, defining internal and external interfaces to connect system elements. Together, functional analysis and system architecture provide a comprehensive system model that is the foundation for successful development.

1. SYSTEMS ENGINEERING
FUNCTIONAL ANALYSIS & SYSTEM ARCHITECTURE
IGAL BEILIN, SYSTEMS ENGINEERING EXPERT

2. WHAT IS FUNCTIONAL ANALYSIS?
Definition of the System from the point of view of its functionality -
originating from User Needs, Use Cases and Operational Concept.
Vs. the outdated and flawed “Physical decomposition first”
approach.
The Functional Analysis approach makes sure we build the system
with exactly what users need, and get it right on first try
(or at least much faster)

3. MAIN STEPS IN FUNCTIONAL ANALYSIS
Define the System’s main functions first
Define the System’s States and Modes (of operation)
Allocate functions to specific States & Modes
Create an Enhanced Function Flow Block Diagram
(EFFBD)

4. FUNCTIONAL ANALYSIS DIAGRAM
Breakdown to main modes of operation and functions
Mode 1
Function 1, Function 2
Mode 2
Function 3, Function 4
Mode 3
Function 5
System Functionality
Main Function /
Objective
Sub state 2.1
Function 2.1.1
Sub state 2.2
Function 2.2.1

5. ENHANCED FUNCTION FLOW BLOCK DIAGRAM - EFFBD
• Functional flow
• Trigger events
Function 1
entry / Trigger 1; Dataset 1
do / Perform Function 1
exit / Output 1
Ref. In Ref. Out
OR IT
Mode 1
Function 2
entry / Output 1; Dataset 2
do / Perform Function 2
exit / Output 2
Function 3
entry / Trigger 2
do / Perform Function 3
exit / Output 3
Function 4
entry / Output 3
do / Perform Function 4
exit / Output 4
Function 5
entry / Dataset 3
do / Perform Function 5
exit / Output 5
Mode 2 IT OR
Feedback/ Iterative process loop
Mode 3
• Input/Output
✓Full functional definition

6. SYSTEM ARCHITECTURE
•Physical decomposition of the system into modules &
components
•Internal & external interface definition: connecting the
system components with flow of data/matter/energy/etc.

7. SYSTEM ARCHITECTURE - DECOMPOSITION
Module 1
-Attribute 1: Type
-Attribute 2: Type
-Attribute 3: Type
+ Operation 1 ()
+ Operation 2 ()
Subsystem 1
-Attribute 1: Type
-Attribute 2: Type
-Attribute 3: Type
+ Operation 1 ()
+ Operation 2 ()
Module 2
-Attribute 1: Type
-Attribute 2: Type
-Attribute 3: Type
+ Operation 1 ()
+ Operation 2 ()
Module 1.1
-Attribute 1: Type
-Attribute 2: Type
-Attribute 3: Type
+ Operation 1 ()
+ Operation 2 ()
Module 1.2
-Attribute 1: Type
-Attribute 2: Type
-Attribute 3: Type
+ Operation 1 ()
+ Operation 2 ()
System
Main System operation

8. SYSTEM ARCHITECTURE – INTERNAL BLOCK DIAGRAM
IBD
System Boundary
Module 1
-Attribute 1: Type
-Attribute 2: Type
-Attribute 3: Type
+ Function 1 ()
Subsystem 1
-Attribute 1: Type
-Attribute 2: Type
-Attribute 3: Type
+ Function 4 ()
Module 2
-Attribute 1: Type
-Attribute 2: Type
-Attribute 3: Type
+ Function 2 ()
Module 1.1
-Attribute 1: Type
-Attribute 2: Type
-Attribute 3: Type
+ Function 5 ()
+ Function 6 ()
Module 1.2
-Attribute 1: Type
-Attribute 2: Type
-Attribute 3: Type
+ Function 7 ()
In.Interface M1-M2 {Power: Voltage}
Ex.Interface 1
Composed off
Composed off
Ex.Interface 1.1
In.Interface M2-M1.1 {Comm. Data}
In.Interface M1-S1 {Power: Voltage}

9. SUMMARY
Functions definition comes first.
Functional Analysis and Architecture definition complement
each other to create a full, comprehensive system model.
Complete Architecture definition, accompanied by quality
requirements, are the foundation for successful System
development.
When we connect the pieces right, the whole is so much more
than the sum of its pieces.

10. INTERESTED & WANT TO LEARN MORE?
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Igal Beilin – Systems Engineering enthusiast