NHibernate single column id that refererences another object -

I have a class whose primary key is a column, which is a reference to the single column primary key of another object. The only way to see it in NHibernate is to pretend that it is a composite key (even if it is a column key) and using key-reference mapping. Is there any more appropriate way?

Bottom Snippet:

  Category Company Export Carteria Public Company Company {Receive; Set; } Class company public string id {get; Set; } COMPANY_EXPORT_CRITERIA table (COMPANY_ID) as the company table (as ID PK) - Company map for CompanyExportCriteria map. 
 
 PS - I'm using the NHibernate fluid for mapping. 

Here is a link to one-to-one mapping documentation for Fluent NBibernate:

Here's the same thing for NHibernate:

You should not need an overall key.

>