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11 The Worklet Service 297
...
</ruleNode>
</task>
</selection>
<constraints>
<case>
<pre>
<ruleNode>
<id>0</id>
<parent>-1</parent>
<trueChild>1</trueChild>
<falseChild>-1</falseChild>
<condition>True</condition>
<conclusion>null</conclusion>
<cornerstone></cornerstone>
<description>root level default node</description>
</ruleNode>
<ruleNode>
<id>1</id>
<parent>0</parent>
<trueChild>-1</trueChild>
<falseChild>-1</falseChild>
<condition>paid = true</condition>
<conclusion>
<_1>
<action>remove</action>
<target>case</target>
</_1>
</conclusion>
...
</case>
</constraints>
</spec>
Listing 11.1 Excerpt of a rules file

to create and manage one or more CheckedOutChildItems, which hold information
about worklet selection, data associated with the work item, and the results of rules
searches.
The WorkletService object, for each work item that is checked out from the
engine, also loads from file the set of rules pertaining to the specification of which
the work item is a member into an RdrSet object. At any time, there may be a num-
ber of RdrSets loaded into the service, one for each specification for which a work
item has been checked out. Each RdrSet manages one or more RdrTree objects, each
tree representing the rule tree for a particular task within the specification, of which
this work item is an instance. In turn, each RdrTree owns a number of RdrNode
objects, which contain the actual rules, conclusions, and other data for each node of
theruletree.
When a rule tree is evaluated against the data set of a work item, each of the
associated nodes of that tree has its condition evaluated by the ConditionEvaluator
object, which returns the boolean result to the node, allowing it to traverse to its true
or false branch as necessary. Finally, the WorkletGateway object provides commu-
nications via a JSP/Servlet interface between the service, the various servlet pages,
and the Rules Editor (see Sect. 11.10.2 for more details).