In this case, you have to provide an access strategy to tell NHibernate how to get and set the property value. The "nosetter" access strategy looks like the one you need. Depending on the naming convention you are using, you may need to specify the naming strategy as well. What you actually need is
Code:
<property ... access="access-strategy.naming-strategy" />
Related information can be found in NHiberanate Documentation at
http://www.hibernate.org/hib_docs/nhibernate/1.2/reference/en/html/mapping.html#mapping-declaration-property. Table 5.1 and 5.2 tell you the access and naming strategy respectively.