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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