ID property for generated data - NHibernate

I have some stored procedures which I am using to create reports (each SP groups the data into days / weeks / months / years). By means of an examp开发者_如何学编程le, I have created a simple entity "Report" which matches the fields from the SP but an error is thrown saying that an ID (or Composite ID) is required.

How can I define an ID for what is a generated dataset and does not map to an actual table?

The mapping file I have is:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
    <class name="Report, Business" mutable="false" check="none">
        <property name="Year" type="int" />
        <property name="Week" type="int" />
        <property name="Date" type="DateTime" />
        <property name="Count" type="int" />
    </class>
    <sql-query name="spReport">
        <return class="Report, Business" lock-mode="read">
            <return-property column="Year" name="Year" />
            <return-property column="Week" name="Week" />
            <return-property column="Date" name="Date" />
            <return-property column="Count" name="Count" />
        </return>
        exec spReport :StartDate, :EndDate
    </sql-query>    
</hibernate-mapping>

Any help is greatly appreciated.

Thanks.

---

<class name="Report, Business" mutable="false" check="none">
  <composite-id>
    <key-property name="Year" type="int" />
    <key-property name="Week" type="int" />
    <key-property name="Date" type="DateTime" />
    <key-property name="Count" type="int" />
  </composite-id>
</class>

You'll have to override Equals and GetHashCode in Report.

Personally, I don't like this approach. It's better not to map the class at all and use SetTransformer(Transformers.AliasToBean<Report>()) on the query.