﻿ Decision Table Hit Policy | Enterprise Architect User Guide

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# Decision Table Hit Policy

The Hit Policy specifies the result of the Decision table in cases of overlapping rules. The single character in a particular Decision table cell indicates the table type and unambiguously reflects the decision logic.

Single Hit Policies:

• Unique: no overlap is possible and all rules are disjoint; only a single rule can be matched (this is the default)
• Any: there might be overlap, but all the matching rules show equal output entries for each output, so any match can be used
• Priority: multiple rules can match, with different output entries; this policy returns the matching rule with the highest output priority
• First: multiple (overlapping) rules can match, with different output entries; the first hit by rule order is returned

Multiple Hit Policies:

• Output order: returns all hits in decreasing output priority order
• Rule order: returns all hits in rule order
• Collect: returns all hits in arbitrary order; an operator (‘+’, ‘<’, ‘>’, ‘#’) can be added to apply a simple function to the outputs

Collect operators are:

• + (sum): the result of the Decision table is the sum of all the distinct outputs
• < (min): the result of the Decision table is the smallest value of all the outputs
• > (max): the result of the Decision table is the largest value of all the outputs
• # (count): the result of the Decision table is the number of distinct outputs

## Example of Unique hit policy

The 'Unique' hit policy is the most popular type of Decision table and all rules are disjoint.

## Example of Priority hit policy

In a table with the 'Priority' hit policy, multiple rules can match, with different output entries. This policy returns the matching rule with the highest output priority.

NOTE: The list of allowable values is used to define the output priority. Here, the allowable values are listed as INELIGIBLE, ELIGIBLE; which defines INELIGIBLE as having a higher priority than ELIGIBLE.

One possible simulation result might resemble this:

The matching rules are highlighted, but the output from rule 2 is chosen because INELIGIBLE has higher priority than ELIGIBLE.

## Example of Collection-Sum hit policy

For a Decision table with the 'Collect-Sum' (C+) hit policy, the result of the Decision table is the sum of all the distinct outputs.

In this example, the output Partial Score is calculated as 43 + 45 + 45 = 133