Week 7 - Systems
Engineering and
Analysis
Buede Chapter 12 –
Graphical Modeling
Techniques
Left – Systems engineers us a lot of graphical models
which look like state diagrams. If you have to predict
how the pieces of a large system will interact, you need
help visualizing that. This one is a “generative model
for how to create generative models.”
1
Wasson also talks about
modeling
• Mostly scattered by topic – what you are
modeling.
• E.g., Sec 15.2 – System behavioral response
model
• Ch 17 – Use Cases & UML
• Ch 20 – Modeling system and support
operations
• Ch 51 – System modeling and simulation
2
Data, Process, and Behavior Models
• Data Models – relationships among input and
outputs.
• Process Models – define functional decomposition
of the system function and flow of inputs and
outputs for those functions.
• Behavior Models – define the control, activation,
and termination of of system functions needed to
meet performance requirements.
3
Modeling Approaches & Methods
Table 12.1
•
Data Modeling
•
Process Modeling
•
Behavior Modeling
•
Object-oriented Modeling
– Entity-relationship diagrams (ERDs)
– Higraphs
– Data flow diagrams (DFDs)
– IDEF0
– N2 charts
–
–
–
–
–
–
Function flow block diagrams (FFBDs)
Behavior diagrams (BDs)
State-transition diagrams (STDs)
Statecharts
Control flow diagrams (CFDs)
Petri nets (PNs)
– Object modeling technique (OMT)
– Real-time object-oriented modeling (ROOM)
4
Data Flow Diagram Semantics
Process
Customer
Banking
Transactions
Process
Customer
Banking
Transactions
Process
Customer
Banking
Transactions
These are three equally valid representations of a process.
Note a process begins with a verb, just as functions or activities
do in IDEF0.
Customer Notice:
Main Menu
Selection
Double-headed
This is an example of a “data
arcs signify dialog
flow”. Note, it is a noun
between functions
phrase and attached to an arc.
Figure 12.6
5
Context (External Systems)
Diagram in DFD
System
Status
Report
BANK SERVICE
PERSONNEL
CUSTOMERS
Completed
Transaction
Prodcuts
Customer
Notices
(CN)
Customer
Inputs
Employee
ID Info
PROVIDE
AUTOMATED
TELLER
MACHINE
SERVICES FOR
CUSTOMERS
Bank's
Acct. Info
Bank
Supplies
Completed
Trans. Info.
Account
Transaction
Data
BANK
COMPUTER
Figure 12.9
6
N2 Charts – an SE favorite!
Request for Elevator Service
& Entry Support
Request for Emergency
Support
Request for Floor & Exit
Support
1.0
Modified Elevator
Configuration & Expected
Ussage Patterns
Electric Power & Emergency
Communication Response
Government Regulations
Passenger Characteristics
Structural Support, Alarm
Signals & Building
Environment
·Digitized Passenger
Requests
Government Regulations
Service, Tests & Repairs
·Sensed Malfunctions
Accept Passenger Requests
& Provide Feedback
2.0
·Assignments for Elevator
Cars
Acknowledgment that
Request Was Received &
Status Information
Emergency Support
·Sensed Malfunctions
Control Elevator Cars
·Elevator Position & Direction
·Elevator Position & Direction 3.0
·Sensed Malfunctions
Move Passengers Between
Floors
·Temporary Modification to
Elevator Configuration
4.0
Elevator Entry Opportunity
Elevator Exit Opportunity
Passenger Environment
Diagnostic & Status
Messages
Enable Effective Maintenance
& Servicing
Figure 12.10
7
Function Flow Block Diagrams
• Basic
–
–
–
–
1
Ref.
2
Perform
Integration
Activities
Perform Design
Activities
Series
Concurrent
Selection
Multiple-exit function
Series
• Enhanced
– Iteration
– Looping
– Replication
Ref.
Concurrent
1.1
Perform
System Level
Design Activities
1.2
Ref.
AND
Perform
Subsystem
Level Design ...
2
AND
Perform
Integration
Activities
1.3
Perform
Component
Level Design ...
Figure 12.11-12
8
Selection & Multiple-exit Functions,
Iteration, Looping in FFBD
for each subsystem
if deficiency is fixed or redesigned
1
Perform Desig n
Activities
2.3.1
IT
LP
cleared subsystem
2.3.6
Inspect & Test
Subsystem
OR
deficient subsystem
2.3.2
Identify & Fix
Correctable
Deficiencies
correctable def.
2.3.3
Assess Impact
of
Uncorrectable...
2.1
Perform
Component
Integration
IT
Modify Baseline
acceptable impact
OR
2.3.4
unacceptable impact
Figure 12.13
Integrate with
Next Subsystem
2.3.5
OR
uncorrectable def
LP
Redesign
Subsystem
9
FFBD for Elevator
1.0
Accept
Passenger
Requests & P...
2.0
Control Elevator
Cars
Ref.
AND
AND
Ref.
3.0
Move
Passengers
Between Floors
4.0
Enable Effective
Maintenance &
Servicing
10
Elevator Functional Architecture
USED AT:
George Mason
Univ.
DATE: 09/29/1999
REV:
AUTHOR: Dennis Buede
PROJECT: Elevator Case Study
x
NOTES: 1 2 3 4 5 6 7 8 9 10
Up Service Request,
Floor Request,
Request to Extend
Entry support
Up Service Request,
Floor Request
Comm. about
Emergency,
Passenger Weight
Characteristics,
Sensed Passenger
Heat Loss/Gain
WORKING
DRAFT
RECOMMENDED
PUBLICATION
Fire Alarm Signal
Signal for Partial Maint. Mode,
Signal for Full Op'g Mode
Request to Extend
Entry support
ACCEPT
PASSENGER
REQUESTS &
PROVIDE
FEEDBACK
DATE
Fire Alarm
A1
CONTROL
ELEVATOR
CARS
Operating
Mode
A2
Electric
Power
MOVE
PASSENGERS
BETWEEN
FLOORS
Relayed Info
about Emergency,
Electric Power,
Sensed Building
Heat
Elevator
Position &
Direction
Entry/Exit Opp'y
Ending Signal;
Capacity
Exceeded Signal
Maint. Action,
Diagnosis Signals,
Repairs,
Test Signals
NODE:
A0
Sensed Malfunctions,
Diagnosis &
Test Responses
Feedback:
Service Request Recieved,
Floor Request Received,
Car On Way,
Door Opening,
Door Closing,
Floor Where Stopped,
About Emergency;
Fire Alarm;
Entry/Exit Opp'y
Ending Signal;
Capacity
Exceeded Signal
Elevator Entry/Exit
Opportunity,
Information about
Emergency,
Elevator Heat
Loss/Gain
Emergency
Comm'n
A3
Electric
Power
CONT EXT :
A-0
Feedback:
Service Request Recieved,
Floor Request Received,
Car On Way,
Door Opening,
Door Closing,
Floor Where Stopped,
About Emergency;
Temporary
Modificatin to
Elevator
Configuration
Assignments
for Elevator
Cars
Digitized
Passenger
Requests
READER
ENABLE
EFFECTIVE
MAINTENANCE
& SERVICING
A4
Malfunction
Signal
Diagnosis Response,
Test Response
Diagnosis Signals,
Maint. Action,
Repairs,
Test Signals
TITLE:
PROVIDE ELEVATOR SERVICES
NUMBER:
P. 3
11
Behavior Diagrams
Update
Position
Updated
Track
No Track
Update
Dropped
Track
Detections
Depleted
Update
Display
Updated
Display
Current
Track
@
Update
Position
Track Update
Update
Display
Detection
Data
Update
Position
Updated
Track
Updated
Display
Current
Track
Detection
Data
Current
Track
Detection
Data
Looping
Selection
Sequence
Remaining
Detections
G
@
+
Updated
Track
L
All tracks
Iteration
@*
Replication
Concurrency
All detections
@*
Current
Track
Detection
Data
All tracks
Detection
Data
@*
@*
Figure 12.14
Updated
Track
Update
Position
Update
Display
Update
Position
All tracks
@*
Updated
Track
Current
Track
&*
Current
Track
Update
Position
@*
@*
Updated
Display
&
Detection
Data
Updated
Track
Update
Display
&
&*
Updated
Display
Updated
Display
Update
Display
@*
12
Finite State Machines
• Finite state machines:
discrete valued inputs,
outputs and internal items
– Sequential: past inputs
impact current outputs
(e.g., state-transition
diagram)
– Combinational: current
outputs characterized
only current inputs
Machines
Continuous or
Analog Machines
Finite State
Machines (FSMs)
Combinational
FSM
Sequential
FSM
• Continuous machines:
continuous and discrete
inputs, outputs and
internal items
Figure 12.16
13
State-transition Diagram for ATM
IDLE
Cust. ID Presented
Process ID for Validity
Event
Output
Unread Cust. ID
CN:”ID Unreadable”
WAITING FOR
CUSTOMER
IDENTIFICATION
Cust. ID Read
CN:”Enter Access Code”
Invalid Access Code
CN:”Please Re-enter”
WAITING FOR
CUSTOMER’S
ACCESS CODE
3rd Invalid Access Code
CN:”Transaction Terminated”
Access Code Validated
CN:”Main Menu Choices”
WAITING FOR
CUSTOMER’S
CHOICE
DEPOSIT
Figure 12.17
WITHDRAWL
TRANSFER
ACCOUNT
BALANCE
14
State-transition Diagram
for an Elevator
Elevator Idle,
Door Open
No Request
Maintain Open Door
Up Request
Close Door
Preparing To
Move Up
Down Request
Close Door
Up Request
Close Door
Door Closed
Up Indicator
Elevator
Starting
Preparing To
Move Down
Down Request
Close Door
Door Closed
Down Indicator
Acceleration > 0
Departed Floor
Elevator
Moving
Near Requested Floor
Slowing
Door Opened
Direction Indicator
Elevator
Enabling Entry/Exit
Elevator
Stopping
Elevator Stopped
Door Activated
Elevator
Door Opening
Pause Timer Elapsed
Destination Query
Checking Next
Destination
Figure 12.18
15
Statechart
SUPERSYSTEM
CCS
HUMAN
w
b
OFF
m
External System Statechart
For Cruise Control System
b
NOT OFF
DRIVE
b
DRIVE
w( b)
AUTOMOBILE
b
ON
OFF
b
ARC LABEL
b
b hat
m
w
DEFINITION
turn on car
turn off car
accident occurs
depress on/off button
X
Figure 12.19
16
Statechart, cntd
NOT OFF
SYSTEM STATUS
INDICATOR
ON
Decomposition of the
“Not Off” State
For Cruise Control System
DEAD
vs
c
ALIVE
u
STANDBY
e
f
vr
d
ARC LABEL
c
d
e
f
u
vr
vs
Figure 12.20
DEFINITION
circuit closed (good bulb or fuse)
circuit open ( bad bulb or fuse)
brake depressed
clutch depressed
wheel revolutions > 7920/ (pi*r) where r
is the wheel radius in inches
push button to resume / set
push CCS button to standby
17
Statechart, cntd
ALIVE
OFF
ON
Decomposition of the
“Alive” State
for the Indicator
of Cruise Control System
w
vs
vr
BLINK
w
w
f
e
ARC LABEL
e
f
vr
vs
w
Figure 12.21
DEFINITION
brake depressed
clutch depressed
push button to resume / set
push CCS button to standby
depress on/off button
18
Statechart, cntd
ON
MAINTAIN
PULSE
h
h
k
DECELERATE j
v
v
i
ACCELERATE
va
vd
k
Decomposition of the
“On” State
for the Indicator
of Cruise Control System
vd
H
va
vr
ARC LABEL
h
h(hat)
i
j
k
v(hat)
va
vd
vr
Figure 12.22
DEFINITION
non drive wheel RPM not equal to drive wheel RPM
non drive wheel RPM equal to drive wheel RPM
wheel RPM decrease from set speed
wheel RPM increase from set speed
wheel RPM match to set speed
release the CCS button
push CCS button to accelerate
push CCS button to decelerate
push button to resume / set
19
Statechart for Cruise Control System
CCS
w
OFF
NOT OFF
b
ON
PULSE
MAINTAIN
h
w
h
m
v
vd
va
DECELERATE j
k
v
i
INDICATOR
k
ACCELERATE
ALIVE
ON
va
f
w
vr
e
OFF
H
vd
vs
c
DEAD
vr
u
STANDBY
BLINK
d
MEMORY
SET
e
f
vs
MEMORY
CLEAR
va
w
v
w
Figure 12.23
20
Object-oriented Modeling –
our favorite in software?
• Object Modeling Technique (OMT)
– Object model (ERD)
– Dynamic model (STD & nested state diagrams)
– Functional model (DFD)
• Real-time Object-oriented Modeling (ROOM)
– Objects = Actors
– Actors communicate via messages
– ROOMcharts
• Combine functional and behavioral models
• Generalization of Statecharts
• Unified Modeling Language (UML) (SysML)
21