Dieser Markierungsausdruck gibt an, dass die Ableitung des Attributs für konkrete Unterklassen (oder eine deren Superklassen) angegeben werden muss.
Falls eines oder mehrere Attribute in einer Regelklasse mit abstract gekennzeichnet sind, erfordert es der CER-Regelwerkvalidierer, dass auch die Klasse selbst mit abstract="true" gekennzeichnet ist, und verhindert die Verwendung der Regelklasse in Ausdrücken "create" (siehe Abschnitt create).
<?xml version="1.0" encoding="UTF-8"?>
<RuleSet name="Example_abstract"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation=
"http://www.curamsoftware.com/CreoleRulesSchema.xsd">
<!-- Base class for all types of benefit.
Every concrete subclass has its own
calculation of "name" and "isEligible". -->
<Class name="Benefit" abstract="true">
<Initialization>
<!-- The person for which benefit eligibility
is being determined. -->
<Attribute name="person">
<type>
<ruleclass name="Person"/>
</type>
</Attribute>
</Initialization>
<!-- The name of this type of benefit -->
<Attribute name="name">
<type>
<javaclass name="String"/>
</type>
<derivation>
<abstract/>
</derivation>
</Attribute>
<!-- Whether the person is eligible for this benefit. -->
<Attribute name="isEligible">
<type>
<javaclass name="Boolean"/>
</type>
<derivation>
<abstract/>
</derivation>
</Attribute>
</Class>
<!-- A concrete subclass of Benefit.
Contains concrete derivations for the inherited
abstract attributes. -->
<Class name="MedicalBenefit" extends="Benefit">
<Attribute name="name">
<type>
<javaclass name="String"/>
</type>
<derivation>
<String value="Medical Benefit"/>
</derivation>
</Attribute>
<Attribute name="isEligible">
<type>
<javaclass name="Boolean"/>
</type>
<derivation>
<all>
<fixedlist>
<listof>
<javaclass name="Boolean"/>
</listof>
<members>
<!-- NB the person attribute is inherited from Benefit
-->
<reference attribute="isPoor">
<reference attribute="person"/>
</reference>
<reference attribute="isSick">
<reference attribute="person"/>
</reference>
</members>
</fixedlist>
</all>
</derivation>
</Attribute>
</Class>
<!-- Another concrete subclass of Benefit,
with different concrete derivations for the inherited
abstract attributes. -->
<Class name="NeedyBenefit" extends="Benefit">
<Attribute name="name">
<type>
<javaclass name="String"/>
</type>
<derivation>
<String value="Medical Benefit"/>
</derivation>
</Attribute>
<Attribute name="isEligible">
<type>
<javaclass name="Boolean"/>
</type>
<derivation>
<all>
<fixedlist>
<listof>
<javaclass name="Boolean"/>
</listof>
<members>
<reference attribute="isPoor">
<reference attribute="person"/>
</reference>
<any>
<fixedlist>
<listof>
<javaclass name="Boolean"/>
</listof>
<members>
<reference attribute="isHungry">
<reference attribute="person"/>
</reference>
<reference attribute="isDeprived">
<reference attribute="person"/>
</reference>
</members>
</fixedlist>
</any>
</members>
</fixedlist>
</all>
</derivation>
</Attribute>
</Class>
<Class name="Person">
<Attribute name="isPoor">
<type>
<javaclass name="Boolean"/>
</type>
<derivation>
<specified/>
</derivation>
</Attribute>
<Attribute name="isSick">
<type>
<javaclass name="Boolean"/>
</type>
<derivation>
<specified/>
</derivation>
</Attribute>
<Attribute name="isHungry">
<type>
<javaclass name="Boolean"/>
</type>
<derivation>
<specified/>
</derivation>
</Attribute>
<Attribute name="isDeprived">
<type>
<javaclass name="Boolean"/>
</type>
<derivation>
<specified/>
</derivation>
</Attribute>
<!-- A list of all the benefits for
which the person is being assessed. -->
<Attribute name="allBenefits">
<type>
<javaclass name="List">
<ruleclass name="Benefit"/>
</javaclass>
</type>
<derivation>
<fixedlist>
<listof>
<ruleclass name="Benefit"/>
</listof>
<members>
<!-- Create instances of the concrete rule classes -->
<create ruleclass="MedicalBenefit">
<this/>
</create>
<create ruleclass="NeedyBenefit">
<this/>
</create>
</members>
</fixedlist>
</derivation>
</Attribute>
<!-- The benefits for which this person
is eligible.
Note that the list is of the abstract
rule class "Benefit", but that each
concrete instance determines its
eligibility in its own way. -->
<Attribute name="eligibleBenefits">
<type>
<javaclass name="List">
<ruleclass name="Benefit"/>
</javaclass>
</type>
<derivation>
<filter>
<list>
<reference attribute="allBenefits"/>
</list>
<listitemexpression>
<reference attribute="isEligible">
<current/>
</reference>
</listitemexpression>
</filter>
</derivation>
</Attribute>
</Class>
</RuleSet>