Hi, I've a problem with table per class hierarchy strategy:

I've a base class NodeACL and the derived classes UserACL, GroupACL.
NodeACL has a property called SecurityObject, which is defined into the other ACL's objects. Infact if you have a UserACL the security object is a User : ISecurityObject and if you have a group the object is a Group : ISecurityObject.

This is my mapping file.... I need to have "SecurityObject" property inside the NodeACL mapping and in all its subclasses... Is it possible?

Thanks!

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Mapping file :
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<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">
<class name="Eureka.Keeper.Security.NodeACL, Eureka.Keeper" table="Keeper_Nodes_ACL">
<id name="Id" access="nosetter.pascalcase-underscore" column="IDACL" type="Int32">
<generator class="identity"/>
</id>
<discriminator column="AllowedType" />
<many-to-one name="Node" access="nosetter.pascalcase-underscore" class="Eureka.Keeper.Node, Eureka.Keeper" column="IDNode" />
<property name="ACLType" access="nosetter.pascalcase-underscore" type="Eureka.Keeper.Security.ACLType, Eureka.Keeper" />

<many-to-one name="SecurityObject" access="nosetter.pascalcase-underscore" class="Eureka.Security.ISecurityObject, Eureka.Core" column="IDAllowed" insert="false" update="false">
</many-to-one>

<subclass name="Eureka.Keeper.Security.UserACL, Eureka.Keeper" discriminator-value="0">
<many-to-one name="SecurityObject" access="nosetter.pascalcase-underscore" class="Eureka.Security.User, Eureka.Core" cascade="none" column="IDAllowed">
</many-to-one>
</subclass>

<subclass name="Eureka.Keeper.Security.GroupACL, Eureka.Keeper" discriminator-value="1">
<many-to-one name="SecurityObject" access="nosetter.pascalcase-underscore" class="Eureka.Security.Group, Eureka.Core" cascade="none" column="IDAllowed">
</many-to-one>
</subclass>

</class>
</hibernate-mapping>

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You can't map an interface since NHib can't instantiate an interface, unless you want it to create a proxy.
You could have an abstract class all your ISecurityObject implementors inherit from and have that class mapped (hbm.xml) with discriminators for the different types. Nhibernate would load the appropriate type for each of your ACL classes' properties (SecurityObject) because they have their own discriminators.