If you're thinking of doing any Business Data Catalog work, do yourself an enormous favour and check out BDC Meta Man.Todd Baginski and Nick Swan have released this extremely useful GUI tool for quickly creating Business Data Catalog application schemas. I used Todd's earlier incarnation as the basis for an import of 10,000 Clarify CRM records . It simplified the process enormously, even in the early goings. Do yourself a favour and check out their work:
http://www.bdcmetaman.com/default.aspx