Decision table is based on logical relationships just as the truth table.
Decision Table is a tool that helps us look at the combination of conditions
Completeness of conditions
Inconsistency of conditions
2.
Components of a Decision Table C1 C2 C3 a1 a2 a3 a4 a5 T T T T F F F F T T F F T T F F T F T F T F T F x x x x x x x x x x x x x x conditions actions values of conditions actions taken R1 R2 R3 R4 R5 R6 R7 R8 rules Read a Decision Table by columns of rules : R1 says when all conditions are T, then actions a1, a2, and a5 occur
The conditions in the decision table may take on any number of values . When it is binary , then the decision table conditions are just like a truth table set of conditions.
The decision table allows the iteration of all the combinations of values of the condition, thus it provides a “completeness check.”
The conditions in the decision table may be interpreted as the inputs of the table , and the actions may be thought of as outputs of the table .
How do you decide how many rules must exist ----- use this to check against Requirements Doc.?
F T T T T T T T T T T - F T T T T T T T T T - - F T T T T T T T T - - - T T T T F F F F - - - T T F F T T F F - - - T F T F T F T F X X X X X X X X X X X Note the Impossible cases Pick input set, <a, b, c>, for each of the columns, or rules, below Assume a, b and c are all between 1 and 200 R1 R2 R3 R4 R5 R7 R6 R9 R8 R11 R10 Explain?
The Calendar next-date problem has many constraints, one of which deals with the value of the month:
Condition 1 : 1 <= month <= 12
Condition 2 : month < 1
Condition 3 : month > 12
8.
A Decision Table for Next-Date Condition 1 Condition 2 Condition 3 Month input T T T T F F F F T T F F T T F F T F T F T F T F There are 2 3 = 8 test conditions (8 columns) for the month value. But ------- are these really “independent” conditions ?
9.
Decision Table for Next-Date Condition 1 Condition 2 Condition 3 Month input T T T T F F F F T T F F T T F F T F T F T F T F Remember : Condition 1: 1 < = m <= 12 Condition 2: m < 1 Condition 3: m > 12 R1 R2 R3 R4 R5 R6 R7 R8 Note that: a) If condition 1 is true, then conditions 2 and 3 must both be false. So Rules 1 – 4 is reduced to just R4. b) If condition 1 is false, then only one of the conditions 2 / 3, not both, can be true. So, rule R5 can be eliminated. c) Not all three conditions can be false. So rule R8 can be eliminated. That leaves only 3 conditions ---- R4, R6, and R7 (resembles “exclusive OR” ?! ) √ √ √
10.
Decision Table for Next-Date with Actions Condition 1 Condition 2 Condition 3 Month input T T T T F F F F T T F F T T F F T F T F T F T F Remember : Condition 1: 1 < = m <= 12 Condition 2: m < 1 Condition 3: m > 12 R1 R2 R3 R4 R5 R6 R7 R8 √ √ √ Action 1 Action 2 - - - X - X X - - - X X - - - - Note that R3 has an action defined in the Decision Table. This should trigger a question because the condition can not happen. There should be no action defined for R3 ---- perhaps, a Specification error ? Assume actions defined in the requirements doc.
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