# 23.4.4\. Content based discrimination ``` <class name="Person" discriminator-value="P"> <id name="id" column="person_id" unsaved-value="0"> <generator class="native"/> </id> <discriminator type="character"> <formula> case when title is not null then 'E' when salesperson is not null then 'C' else 'P' end </formula> </discriminator> <property name="name" not-null="true" length="80"/> <property name="sex" not-null="true" update="false"/> <component name="address"> <property name="address"/> <property name="zip"/> <property name="country"/> </component> <subclass name="Employee" discriminator-value="E"> <property name="title" length="20"/> <property name="salary"/> <many-to-one name="manager"/> </subclass> <subclass name="Customer" discriminator-value="C"> <property name="comments"/> <many-to-one name="salesperson"/> </subclass> </class> ```