Tutorial Using Decision Tables

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Decision Tables

Rules can also be coded in decision tables. This representation is easier to read and write for rule sets that have many rules of a similar form. Using our prior example, these rules:

UnitPrice = 10 When Quantity < 20
UnitPrice = 8 When Quantity >= 20

can be written in a decision table as shown below:

To create a table in a rule set:

• The first row and column must contain the word 'Table' followed by a space separated list of output fact names.
• The second row has column headers for the input and output facts. Each of the output facts must occur, and any number of additional input facts.
• There can be any number of rows of data. The columns for output facts must contain values or expressions that evaluate to a value which will be assigned to the fact.
• The input facts can be values and expressions which are compared to the fact, or can contain the comparison operators >, <, >=, <=, and, or, not.

ARulesXL will draw a single line border around the table after you click outside the rule set. This lets you verify that your tables are set up correctly.

You can intermix rules and decision tables in the same rule set. See the Decision Table.xls sample and the Decision Table Reference for more information.

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