1. Process Descriptions: 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.
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2. Logic Modeling
Text-based process descriptions provide more information about the process than the DFD alone
If the logic underlying the process is quite complex, more detail may be needed in the form of logic model:
Structured English
Decision trees
Decision tables

3. Structured English
Structured English: modified form of English language used to specify the logic of information system processes.
No single standard.
Typically relies on action verbs and noun phrases and contains no adjectives or No specific standards.
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4. Structured English Common Statements Example
Action Statement Profits = Revenues - Expenses
Generate Inventory Report
Add Product record to Product Data Store
If Statement IF Customer Not in Customer Data Store
THEN Add Customer record to Customer Data Store
ELSE Add Current Sale to Customer’s Total Sales
Update Customer record in Customer Data Store
For Statement FOR all Customers in Customer Data Store, do
Generate a new line in the Customer Report
Add Customer’s Total Sales to Report Total
Case Statement CASE
If Income < 10,000: Marginal tax rate = 10%
If Income < 20,000: Marginal tax rate = 20%
If Income < 30,000: Marginal tax rate = 31%
If Income < 40,000: Marginal tax rate = 35%
ELSE Marginal tax rate = 38%
ENDCASE

5. Structured English
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6. Structured English
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7. Decision Trees
Graphical way of depicting if-then-else logic

8. Decision Tables
Represent very complex processes with multiple decision rules
Decision table: a matrix representation of the logic of a decision which specifies the possible conditions for the decision and the resulting actions.
Best used for complicated decision logic.
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9. Decision Tables
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10. Decision Tables
Condition stubs: that part of a decision table that lists the conditions relevant to the decision.
Action stubs: that part of a decision table that lists the actions that result for a given set of conditions.
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11. Decision Tables
Rules: that part of a decision table that specifies which actions are to be followed for a given set of condition.
Indifferent condition: in a decision table, a condition whose value does not affect which actions are taken for two or more rules.
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12. Decision Tables Procedure for Creating Decision Tables
Name the condition and the values that each condition can assume.
Name all possible actions that can occur.
List all possible rules.
Define the actions for each rule.
Simplify the table.
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13. Decision Tables
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14. Deciding Among Structured English and Decision Tables
Criteria
Structured English
Decision Tables
Determining Conditions and Actions
Second Best
Third Best
Transforming Conditions and Actions into Sequence
Best
Checking Consistency and Completeness
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