7. Design 1

Agenda for design activity1. Flow diagrams2. Instrumentation3. State tables4. Decision tables5. Homework

7. Design 2

1. Flow diagramsDefinitionAutomated techniquesFlowing down interfaces

1. Flow diagrams

7. Design 3

Definition (1 of 2)Flow diagrams show the flow of physical

quantities, data, and control into, out of, and through a product. Examples are• Power• Cooling air• Signals• Control

1. Flow diagrams

7. Design 4

Definition (1 of 2)Diagrams can be functional or physicalControlling the flow is one of the strongest

influences a product engineer has on the development of a product

1. Flow diagrams

7. Design 5

Automated techniquesExcel spreadsheetData bases; e.g. TeamWork

1. Flow diagrams

7. Design 6

Flowing down interfacesProduct

requirements

Lower product A requirements

Lower product B requirementsInterface

Product design

concept; e.g.,power control

Product requirements suggest a concept. Design develops this concept and creates requirements

for lower products and I/Fs. The I/F requirements become lower requirements

requirementsrequirements requirements

requirements requirements

1. Flow diagrams

7. Design 7

2. InstrumentationNeed for instrumentationExamples of instrumentationValue of embedding instrumentationCosts of instrumentation

2. Instrumentation

7. Design 8

Need for instrumentationBuild and verify activities benefit from

instrumentationCustomers are wary about depending upon the

results of simulationCustomers feel more comfortable with measured

data

2. Instrumentation

7. Design 9

Examples of instrumentationTime taggingThroughput Trouble shootingAccess to unavailable features

2. Instrumentation

7. Design 10

Value of embedding instrumentationLess expensive than adding laterCommon to leave in the system

2. Instrumentation

7. Design 11

Costs of instrumentationExpensive to collect all variables produced by the

system and then figure out what to do with the data later

Expensive without stated objectiveData reduction expensive

2. Instrumentation

7. Design 12

3. State diagrams Example 1 Logical control requirements in words Complete state diagram Simplified state diagram Number of paths in state diagram Truth table

3. State diagrams

7. Design 13

Example 1

Remote terminal (RT)

1Master

power

buscommunications

self testloading

operation

closed open

RT 1 power switch

Goal -- turn on power. Establish communications, load, and operate

3. State dagrams

7. Design 14

Logical control requirements in wordsTwo power control states

• 1. Off• 2. On

Off when power switch is open.On when power switch is closed

3. State dagrams

7. Design 15

Complete state diagram

1off

2on

RT 1 power switch open

RT 1 power switch closed

RT 1 power switch open

RT 1 power switch closed

Power-state state diagram showing state transition paths and same-state transition paths

Power-state state diagram

transition paths

same- state transition paths

3. State diagrams

7. Design 16

Simplified state diagram

1off

2on

Power switch open

Power switch closed

Power-state state diagram showing only state transition paths and not showing the same-state transition paths.

This form is used often.

Power-state state diagram

3. State diagrams

7. Design 17

Number of paths in a state diagramMaximum number of state transition paths is n2

Maximum number of same-state transition paths is n

Maximum number of state transition paths excluding the same-state transition paths is n2 - n.

Maximum number doesn’t need to be present

3. State diagrams

7. Design 18

Truth table

RT 1 power switch RT 1 power state

open offclosed on

decisions

criterion

A truth table has the same information as a state diagram, but it is less graphic

3. State diagrams

7. Design 19

4. Decision tables (1 of 2) Using decision tables Defining number of decisions Defining the number of paths Defining the number of options per path Example 1 Creating a decision table Defining number of decision tables

4. Decision tables

7. Design 20

Decision tables (2 of 2) Using canonical format Ordering criteria rows Adding results rows Ordering decision columns Checking correctness Example 2 Example 3

4. Decision tables

7. Design 21

Using decision tables (1 of 3)

A decision table is a truth table with the information rearranged to be more compact when typed

RT 1 power-state decision table

Criteria/Decisions 1 2 #Power switch on F T 2

ResultPower state 1 2

Num of decisions 1 1 2

4. Decision tables

7. Design 22

Using decision tables (2 of 3)Identifies all possibilitiesUncovers hidden pathsPromotes consistencyProvides concise documentationAllows numerical checks for quality

4. Decision tables

7. Design 23

Using decision tables (3 of 3)Decision tables don’t guarantee that

the decisions are right

4. Decision tables

7. Design 24

Defining number of decisions (1 of 2)Number of decisions equals the product of the

number of choices for each criterion. Must account for all the decisionsA “-” in a decision table means that the

decision table doesn’t care what the value of a criterion is.

4. Decision tables

7. Design 25

Defining number of decisions (2 of 2)RT 1 power-state Number of

decisions per

criterion

Number of decisions

It’s not necessary to show the number of decisions, but showing the number of decisions helps check

the quality of the table

Criteria/Decisions 1 2 #Power switch on F T 2

ResultPower state 1 2

Num of decisions 1 1 2

4. Decision tables

7. Design 26

Defining the number of pathsRT 1 power-state

It’s not necessary to show the number of paths, but showing the number of paths helps check the quality of the state diagram.

Criteria/Decisions 1 2 #Power switch on F T 2Power state - - 2

ResultPower state 1 2

Num of decisions 2 2 4

Paths from/to 1 21 1 12 1 1 4

Add current state even though not

needed in example

Show the matrix of paths

4. Decision tables

7. Design 27

Defining the number of options

1 2 31 16 2 02 14 3 13 14 2 2

2

1

3

214

1

14

23 2

matrix of options for each path (cell)

total = 54

Matrix of options shows the number of options for each path. Each cell position represents a path

4. Decision tables

7. Design 28

Example 1 (1 of 3)Two communications states

• 1. Not established (not est)• 2. Established (est)

Not established if power state is off or ability to communicate is false

Established if power state is on and ability to communicate is true

4. Decision tables

7. Design 29

Example 1 (2 of 3)

communications not established

communications established

power state = off orability to communicate = false

power state = on andability to communicate = true

4. Decision tables

7. Design 30

Example 1 (3 of 3)

Criteria/Decisions 1 2 3 #Power state = on F T T 2Comm OK - F T 2Comm state - - - 2

ResultComm state 1 1 2

Num of decisions 4 2 2 8

Paths from/to 1 21 3 12 2 2 8

Communications state

4. Decision tables

7. Design 31

Creating a decision table1. Use Excel2. Use ‘- to enter a minus into a cell3. Use calculating capabilities to check

numbers4. Use non-proportional fonts5. Use single character criteria

4. Decision tables

7. Design 32

Defining number of decision tablesUse one state diagram for each decision

or conceptUse one decision table for each diagramUse adjectives to avoid ambiguity

4. Decision tables

7. Design 33

Using canonical format

Criteria/Decisions 1 2 3 4 5 6 7 8 9 10 11 12 #A,B A A A A A A B B B B B B 2C,D,E C C D D E E C C D D E E 3F,G F G F G F G F G F G F G 2

ResultState 1 1 1 1 1 1 2 2 3 4 5 5

Num of decisions 1 1 1 1 1 1 1 1 1 1 1 1 12

Example canonical format

4. Decision tables

7. Design 34

Ordering criteria rows (1 of 3)Listed vertically Based on the author’s guess at the impact of

each criterion on stateStrongest criterion at the topWeakest at the bottom

4. Decision tables

7. Design 35

Ordering criteria rows (2 of 3)Order of the rows can be changedNumber of columns may changeNumber of decisions and the path matrix

remain the sameConfirms accuracy of rearranging rows

4. Decision tables

7. Design 36

Ordering criteria rows (3 of 3)Changing rows doesn’t leave table in

canonical formatRow-order resulting in fewest number

columns is not always obviousObtained by trial and error

4. Decision tables

7. Design 37

Adding results rows

Criteria/Decisions 1 2 3 4 # 1 2 3 #A,B A A B B 2 A A B 2C,D C D C D 2 C D - 2

ResultState 1 1 2 2 1 1 2Create error N Y N N N Y N

Num of decisions 1 1 1 1 4 1 1 1 4

Results in addition to state can be shown. However additional information may prevent merging

some columns.4. Decision tables

7. Design 38

Ordering decision columns (1 of 6)1. Listed from left to right2. Weakest criterion change fastest3. Strongest change slowest

4. Decision tables

7. Design 39

Ordering decision columns (2 of 6)

Criteria/Decisions 1 2 3 4 5 #A,B A B B B B 2C,D,E - C D D E 3F,G - - F G - 2

ResultState 1 2 3 4 5

Num of decisions 6 2 1 1 2 12

Example canonical format

4. Decision tables

7. Design 40

Ordering decision columns (3 of 6)1. Find columns in which criteria have no effect 2. Merge such columns into a single column 3. Replace the values of the criteria that have no

effect with a “-”

4. Decision tables

7. Design 41

Ordering decision columns (4 of 6)The columns must be mutually exclusive

4. Decision tables

7. Design 42

Ordering decision columns (5 of 6)

Criteria/Decisions 1 2 3 # 1 2 3 4 5 #A,B A - B 2 A A A B B 2C,D - C D 2 C D C C D 2

ResultState 1 2 3 1 1 2 2 3

Num of decisions 2 2 1 5 1 1 1 1 1 5

Columns 1 and 2 in the left hand table are not mutually exclusive. Columns 1 and 3 in right hand table are not

mutually exclusive. Results are conflicting.

Left hand Right hand

4. Decision tables

7. Design 43

Ordering decision columns (6 of 6)Not necessary to simplifyMinimizing makes printing the decision table

easier and helps definition and implementation

4. Decision tables

7. Design 44

Checking correctness1. Identify all states2. Identify all criteria3. Identify all values of each criterion4. Enter the criteria values into the table in

canonical formatGuidelines for Creating a DT (2 of 2)5. Determine state corresponding to each

column6. Simplify the decision table7. Confirm the number of decisions

4. Decision tables

7. Design 45

Example 2 (1 of 5)Three load states

• 1. Not loaded or loading• 2. Loading• 3. Loaded

Determined by • Communications state (not est, est -- [F,T])• Load state (1, 2, 3 -- [1, 2,3])• Load command (none, stop, load -- [N, S, L])• Load status (none, failure, complete -- [N, F, C])

4. Decision tables

7. Design 46

Example 2 (2 of 5)If (1) the comm state is not established or (2)

the load status is failure, then the load state is not-loaded-or-loading

If (1) the comm state is established and (2) the load status is not failure and (3) the load command is stop, then the load state is loading

If (1) the comm state is established and (2) the load status is complete and (3) the load command is none and (4) the current load state is loading, then the load state is loaded

4. Decision tables

7. Design 47

Example 2 (3 of 5)

not loadedor loading

(1)comm state = not est

or load status = failurecomm state = est

& load cmnd= load& load status = not failure

comm state = est & load status =complete

loading(2)

loaded(3)

comm state = not estor load status = failure

comm state = est& load cmnd= load

& load status = not failure4. Decision tables

7. Design 48

Example 2 (4 of 5)Criteria/Decisions 1 2 3 4 5 6 7 8 9 10 11 12Comm state F T T T T T T T T T T T 2Load status - F N N N N N C C C C C 3Load command - - N N N S L N N N S L 3Load state - - 1 2 3 - - 1 2 3 - - 3ResultLoad state 1 1 1 2 3 1 2 1 3 3 1 2Num of decisions 27 9 1 1 1 3 3 1 1 1 3 3 54Path 1 to 1 9 3 1 1 1 1 16 1 2 3Path 1 to 2 1 1 2 1 16 2 0Path 1 to 3 0 2 14 3 1Path 2 to 1 9 3 1 1 14 3 14 2 2Path 2 to 2 1 1 1 3Path 2 to 3 1 1Path 3 to 1 9 3 1 1 14Path 3 to 2 1 1 2Path 3 to 3 1 1 2

4. Decision tables

7. Design 49

Example 2 (5 of 5)

Criteria/Decisions 1 2 3 4 5 6 7 #Comm state F - T T T T T 2Load status - F N C N C C 3Load command - - S S L L N 3Load state - - - - - - 2 3

ResultLoad state 1 1 1 1 2 2 3

Num of decisions 27 27 3 3 3 3 1 67

Paths from/to 1 2 31 20 2 2 20 2 13 20 2 67

Problems with developing decision table ad hoc

67>54

4. Decision tables

7. Design 50

Example 3 (1 of 4)Two operate states

• 1. Not operating• 2. Operating

Determined by • Operate command (stop, operate -- [S,O])• Operate state (1, 2-- [1,2])• Load state (not loaded, loading, loaded [1,2,3]

4. Decision tables

7. Design 51

Example 3 (2 of 4)If (a) the operate command is stop, or (b) the

operate command is operate and the loading state is 1 or 2, then the operate state is not operating

If the operate command is operate, then the operate state is operating

4. Decision tables

7. Design 52

Example 3 (3 of 4)

not operating(1)

operating(2)

operate command = operate

operate command = stop

4. Decision tables

7. Design 53

Example 3 (4 of 4)

Criteria/Decisions 1 2 3 4 #Operate command S O O O 2Load state - 1 2 3 3Operate state - - - - 2 ResultOperate state 1 1 1 2

Num of decisions 6 2 2 2 12

Paths from/to 1 21 5 12 5 1 12

4. Decision tables

7. Design 54

5. HomeworkProblemSix statesDetermined byOff stateNot communicating stateNot loaded stateLoading stateLoaded stateOperating state

5. Homework

7. Design 55

Problem

1. Create the decision table for this problem 2. Show the number of decisions for each

column3. Create the path matrix showing the number

of paths between each state and the number of options for taking each path

Hint -- Use Excel to generate the decision table in canonical format using the criteria in the order given, and don’t be intimidated by the words defining the resulting state

5. Homework

7. Design 56

Six States1. Off2. Not communicating3. Not loaded4. Loading5. Loaded6. Operating

5. Homework

7. Design 57

Determined by Power command = on (false, true -- [F,T])Communication status = OK (false, true --

[F,T])Load status (failed, none, complete -- [F, N,

C])Load command (none, stop, load -- [N, S, L])State [1, 2, 3, 4, 5, 6]Operate command (stop, operate [S, O]

5. Homework

7. Design 58

Off StateIf the power command is off, then the state is off

5. Homework

7. Design 59

Not Communicating StateIf (1) the power command is on and (2) the

communication status is false, then the state is not communicating

5. Homework

7. Design 60

Not Loaded StateIf (1) the power command is on and (2) the

communication status is true and (3) either • (a) the load status is failed or • (b) the load status is none and the load

command is none and the state is 1-3, or• (c) the load status is complete and the load

command is none and the state is 1-3, or• (d) the load status is none or complete and

the load command is stop • then the state is not loaded

5. Homework

7. Design 61

Loading StateIf (1) the power command is on and (2) the

communication status is true and (3) either• (a) the load status is none and the load

command is none, and the state is loading or

• (b) the load status is none and the load command is load or

• (c) the load status is complete and the load command is load

• then the state is loading

5. Homework

7. Design 62

Loaded StateIf (1) the power command is on and (2) the

communication status is true and (3) either• (a) the load status is either none or

complete, and the load command is none, and the current state is either loaded or operating, and the operate command is stop

• (b) the load status is complete, and the load command is none, and the current state is loading

• then the state shall be loaded

5. Homework

7. Design 63

Operate StateIf (1) the power command is on, and (2) the

communication status is true and (3) the load status is none or complete, and (4) the load command is none, and (5) the current state is loaded or operating, and (6) the operate command is operate then the state shall be operating

5. Homework