Logic Modeling

Data flow diagrams do not show the logic inside the processes

Logic modeling involves representing internal structure and functionality of processes depicted on a DFD

Logic modeling can also be used to show when processes on a DFD occur

9.19.1

Logic Modeling

Deliverables and Outcomes Structured English Decision Tables Decision Trees State-transition diagrams Sequence diagrams Activity diagrams

9.29.2

Modeling Logic with Structured English

Modified form of English used to specify the logic of information processes

Uses a subset of English Action verbs Noun phrases No adjectives or adverbs

No specific standards

9.39.3

Modeling Logic with Structured English

Similar to programming language If conditions Case statements

Figure 9-3 shows Structured English representation for Hoosier Burger

9.49.4

Modeling Logic with Decision Tables

A matrix representation of the logic of a decision

Specifies the possible conditions and the resulting actions

Best used for complicated decision logic

9.59.5

Modeling Logic withDecision Tables

Consists of three parts Condition stubs

Lists condition relevant to decision Action stubs

Actions that result from a given set of conditions Rules

Specify which actions are to be followed for a given set of conditions

Indifferent Condition Condition whose value does not affect which action is taken

for two or more rules

9.69.6

Developing Decision Tables

Tutorial - http://www.mccombs.utexas.edu/courses/mis374/Bailey/Class20Chpt7PrelimConst/Class20Decision%20Table%20and%20Structured%20EnglishTutorial.doc

Determine the number of conditions that may affect the decision

Determine the number of possible actions that can be taken Determine the number of condition alternatives for each

condition Calculate the maximum number of columns in the decision

table by multiplying the number of alternatives for each condition

Developing Decision Tables (cont.)

5) Fill in the condition alternatives

C1 Y Y Y Y N N N N

C2 Y Y N N Y Y N N

C3 Y N Y N Y N Y N

A1 X X X X X X

A2 X X X X X

Developing Decision Tables (cont.)

6) Combine rules where alternative conditions don’t affect the outcome

C1 Y - Y N N N

C2 Y N N Y Y N

C3 - N Y Y N Y

A1 X X X X

A2 X X X X

Modeling Logic with Decision Trees

A graphical representation of a decision situation

Decision situation points are connected together by arcs and terminate in ovals

Two main components Decision points represented by nodes Actions represented by ovals

9.109.10

Modeling Logic with Decision Trees

Read from left to right

Each node corresponds to a numbered choice on a legend

All possible actions are listed on the far right

9.119.11

Figure 9-9Decision tree representation of the decision logic in the decision tables in Figures 9-4 and 9-5, with only two choices per decision

point

9.129.12

Deciding Among Structured English, Decision Tables and Decision Trees

Criteria Structured English

Decision Tables

Decision Trees

Determining Conditions and Actions

Second Best Third Best Best

Transforming Conditions and Actions into Sequence

Best Third Best Best

Checking Consistency and Completeness

Third Best Best Best

9.139.13

Summary

Several methods of logic modeling Structured English

Primarily communication technique for analysts and users

Decision Tables Conditions are listed in condition stubs Possible actions are listed in action stubs Rules link conditions with actions

9.149.14

Summary

Decision Tables Lists all possible rules

Decision Trees Conditions are portrayed by decision points Values are represented by paths between

decision points and ovals that contain actions

9.159.15

Summary

Comparison of Structured English, Decision Tables and Decision Trees Most studies show that decision trees are

best for many criteria There is no best technique Analyst must be proficient in all three

9.169.16

Writing Instructions

Examples of Actual Instructions

On a bag of Fritos – “You could be a winner! No purchase necessary. Details inside.”Bar of Dial Soap – “Use like regular soap.”Frozen dinner serving suggestion – “Defrost”Hotel-provided shower cap in a box – “Fits one head”

Examples of Actual Instructions

Tesco’s Tiramisu Dessert – “Do not turn upside down.” printed on the bottom of the boxNytol (a sleep aid) – “Warning: may cause drowsiness”Korean kitchen knife – “Warning: keep out of children.”Sainsbury’s Peanuts – “Warning: contains nuts.”Chinese-made Christmas lights – “For indoor or outdoor use only.”

Instructions

Instructions are everywhere

Instructions have the power to get people to perform important actions

Good instructions create value

Building Blocks of Actionable Instructions

Good instructions contain the following:

Purpose (reason)

Objective (destination)

Core (procedure)

Time (duration)

Expectation (anticipation)

Failure (error)

Example

We’d like you to come to our house next Friday. (destination) We’re having a dinner party to celebrate our anniversary. (reason) Our address is 1015 Forest. Get off at the Oak Park exit on the Eisenhower Expressway. (procedure) The drive should take about 35 minutes in moderate traffic. (duration) On the expressway, you will pass Central Avenue and then Austin before you come to Oak Park. (anticipation) If you see the exit for River Forest, you’ve gone too far. (error)