Can a purchase and sale agreement assign IP rights without attending specifics?

If a main agreement (purchase and sale, for example) calls for a general assignment of IP rights, is that enough for a true assignment to have taken place?

IPKat has an interesting discussion of this issue. One suggestion is “to provide an exhibit [for] each of the defined IP Rights that describes with particularity the IP rights of the assignor that are being assigned,” and have the main agreement stipulate that the parties will execute the documents exhibited as an IP assignment and transfer.

Analysts encountering this situation in due diligence need to make sure the details of an IP assignment document are consistent with the main agreement.