The Biztalk Base EDI Adapter is limited by the number of X12 and EDIFACT document versions it supports.
This KB article is written for Biztalk 2004 but applies to Biztalk 2006 as well.
[url]http://support.microsoft.com/?id=840113[/url]
You can create your own EDI schemas for messages not supported by the base adapter. Apparently this is not a simple task.
[url]http://msdn.microsoft.com/library/default.asp?url=/library/en-us/BTS06Operations/html/35226250-c497-467c-a9d0-64efc040e227.asp[/url]
The MS recommended approach is to buy the Covast EDI Acccelerator if Base EDI Adapter does not support the message formats you need.