PowerDesigner provides support for generating for NHibernate through an extended model definition.
Verify that the current model has the target language C# 2.0 or Visual Basic 2005
Select Model > Extended Model Definitions, and click the Import tool.
Click the O/R Mapping sub-tab, select the NHibernatexem, and click OK to attach it to your model.
Click OK to close the List of Extended Model Definitions and return to your model.
Note:
You can also attach an XEM at model creation time by clicking the Select Extensions button on the New Model dialog.
NHibernate Options
To set the database connection parameters and other NHibernate options, double-click the model name in the browser to open its property sheet, and click the NHibernate tab.