More about Decision Tree rules
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Decision tree evaluation may be based on a known property identified on the Input tab, or on a parameter supplied in the Property-Map-DecisionTree method, or both.
If you leave the Property field blank, evaluation is always based on the parameter. If a parameter is supplied, the parameter value is used even when the Property field is not blank.
As an alternative to the Property-Map-DecisionTree method, you can use these standard functions to evaluate a decision tree rule:
@(Pega-RULES:DecisionTree).ObtainValue(tools, myStepPage, decisiontree, inputproperty)
@(Pega-RULES:DecisionTree).ObtainValue(tools, myStepPage, decisiontree, inputproperty, bAllowMissingProperties)
Decision tree rules can also be evaluated as part of a collection rule (Rule-Declare-Collection rule type). C-2547
See Pega Developer Network article 
PRKB-8707 How to evaluate a decision tree rule and handle
errors for an example.
You can create a decision tree rule by importing (or "harvesting) a specially formatted text file. This capability lets others not familiar with Process Commander create decision tree rules. See About the Rule from File wizard.
Process Commander does not limit the
number of nodes in a decision tree rule. However, as a best practice to
avoid slow performance when updating the form and also avoid the Java
64KB code maximum, limit your decision tree rules to no more than 300 to
500 rows. MARTT 6/21/07 clinic
When you save a decision tree rule, the system converts the rule to Java source code. As a learning or debugging aid, you can review this Java code.
C-1665Click the Show Java toolbar button (
) to see the system-generated
Java code that implements the rule. The window presents a read-only
preview of the Java that implements this rule instance. This Java code is
not identical to the Java that is executed at runtime, which includes
Java code inlined from other rule instances and reflects rules in the
requestor's RuleSet list.
When a Declare Expression rule has Result of decision
tree for the Set Property To field, special
processing occurs at runtime when a property referenced in the decision
table rule is not present on the clipboard. Ordinarily such decision
rules fail with an error message; in this case the
Otherwise value is returned instead. For details, see
Pega Developer Network article PRKB-20805 Troubleshooting:
Declarative Expression does not execute when a decision rule provides no
return value.B-18749
Despite the class name, the Rule-Declare-DecisionTable rule type does not produce forward or backward chaining. Technically, it is not a declarative rule type.
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decision shape |
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Property-Map-DecisionTree method
Debugging with the Tracer |