Business Data Connectivity Model based on Contact

I'm trying to create a .NET assembly connector for BDC. I'm creating the Business Data Connectivity Model and I'd like my entity to behave in SharePoint as a contact - so that I could use "Connect to Outlook" on the external list that I will create based on this external content type. But I cannot find any information on how to specify that this entity derives from or is based on Contacts. What should I do?