More about Map Value rules

Map value rules can be updated as needed to reflect changing business conditions, without the need to ask a skilled developer to modify complex activities or other rules.

Uploading an Excel spreadsheet to start

If you have in advance an Excel spreadsheet (XLS file) that contains useful starting information for a map value rule, you can incorporate (or "harvest") the XLS file and the information it contains directly into the new rule. See About the Rule from File wizard.

Evaluating

Both rows and columns contain a Type field (set on the Headers tab). The system makes comparisons according to the data type you recorded on the Headers tab, converting both the input and the conditions to the specified data type.

At runtime, the system evaluates row conditions first from top to bottom, until one is found to be true. It then evaluates column conditions for that row, left to right, until one is found to be true. It returns the value computed from that matrix cell.

Where map value rules are used

You can reference map value rules in five places:

• On the Visio diagram for a flow, the shape identifies a decision task that is associated with a map value. At runtime, the flow proceeds along one of the connectors from this shape based on the results of the translated value.
• In activities that use the Property-Map-Value method or the Property-Map-ValuePair method. These methods evaluate a one-dimensional or two-dimensional map value, compute the result, and store the result as a value for a property.
• In other map value rules, through a Call keyword in a cell.
• Through a standard function ObtainValuePair() in the Pega-RULES:Map library.
• On the Collection tab of a collection rule.

Input parameters in called map values rules

If a map value rule is evaluated through a decision shape on a flow, or one of the two methods noted above, the input value or values may be literal constants or may be property references, recorded in the flow or in the method parameters.

However, if a map value rule is evaluated by a Call from a cell in another map value rule, the evaluation always uses the Input Property on the Header tab. Nothing in the Call can override this source.

Special processing with Declare Expression calls

When a Declare Expression rule has Result of map value 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 Default 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.

Performance

Process Commander does not limit the number of nodes in a map value 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.

Java code display

When you save a map value rule, the system converts the rule to Java source code. As a learning or debugging aid, you can review this Java code.

Click the Show Java toolbar button () to see the system-generated Java code that implements the map value logic. 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 executes at runtime, which includes Java code inlined from other rule instances and reflects rules in the requestor's RuleSet list.

Parent class

Through directed inheritance, the immediate parent of the Rule-Obj-MapValue class is the Rule-Declare- class. However, despite the class structure, this rule type does not produce forward or backward chaining. Technically, it is not a declarative rule type.

	decision task
	Property-Map-Value method Property-Map-Value-Pair method
	Atlas — Standard Map View rules

About Map Value rules