1. Seg3430A Tutorial 8 Decision Table

2. 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 For example, Structured English, Decision Tables, Decision Trees, State-transition diagrams, Sequence diagrams, Activity diagrams

3. Modeling Logic with Decision Tables Decision Table –A matrix representation of the logic of the decision –Specifies the possible conditions and the resulting actions. –Best used for complicated decision logic Consists of three parts –Condition stubs: lists the conditions to the decision –Action stubs: lists the actions that result for a given set of conditions –Rules: specifies which actions are to be followed for a given set of conditions

4. Decision Table Methodology Step 1: Identify conditions and values –Find condition tests and all of the values Step 2: Compute Max Number of Rules –Multiply the number of values for each condition Step 3: Identify possible actions –Determine independent actions to be taken Step 4: Enter all possible rules –Fill in the values of the conditions in each numbered rule column Step 5: Define actions for each Rule –Mark the appropriate actions with X Step 6: Verify the policy –Review the decision table with end-users Step 7: Simplify the table –Eliminate and/or consolidate rules

5. An Example Scenario: –A marketing company wishes to construct a decision table to decide how to treat clients according to three characteristics: Gender, City Dweller, and age group: A (under 30), B (between 30 and 60), C (over 60). The company has four products (W, X, Y and Z) to test market. Product W will appeal to female city dwellers. Product X will appeal to young females. Product Y will appeal to Male middle aged shoppers who do not live in cities. Product Z will appeal to all but not the older females.

6. An Example Step 1: Three conditions &values: –GenderF/M –CityY/N –Age groupA/B/C Step 2: –Max. num. of rules = 2x2x3 = 12 Step 3: Five actions –Market product W –Market product X –Market product Y –Market product Z –Do not market product

7. An Example Step 4 & Step 5: : Conditions123456789101112 GenderFMFMFMFMFMFM CityYYNNYYNNYYNN Age groupAAAABBBBCCCC Actions Market WXXX Market XXX Market YX Market ZXXXXXXXXXX Don’t marketX

8. Simplify Decision Table Remove impossible rules Eliminate indifferent conditions –An indifferent condition is a condition whose values do not affect the decision and always result in the same action. –These rules can be consolidated into a single rule Simplify unclear rules or actions

9. An Example 12345678 Condition-1YYYYNNNN Condition-2YYNNYYNN Condition-3YNYNYNYN Action-1X Action-2X Action-3XXX ImpossibleXXX

10. An Example Eliminate impossible rules 12345 Condition-1YNNNN Condition-2YYYNN Condition-3YYNYN Action-1X Action-2X Action-3XXX

11. An Example Merge rule 4 and 5 to form 4’ 1234’ Condition-1YNNN Condition-2YYYN Condition-3YYN- Action-1X Action-2X Action-3XX

12. An Example Simplify unclear rules 1’234’ Condition-1YNNN Condition-2-YYN Condition-3-YN- Action-1X Action-2X Action-3XX