Post on 21-Dec-2015
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
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)