Such an upgrade could be quite expensive for users of older SAP products like R/3, said David Dobrin, an analyst at B2B Analysts Inc. in Cambridge, Mass.

Because mySAP ERP 2005 requires NetWeaver to function, many customers will have to pay a premium to upgrade from older SAP applications, he said.

SAP executives have said that they won't force any customers to use NetWeaver and noted that it's an open, standards-based architecture.

Aaron Nichols, a general manager of IT at Canada Post Corp. in Ottawa, said he's concerned that NetWeaver brings SAP into new businesses, such as Web services and enterprise application integration. Canada Post has used middleware from BEA Systems Inc. to support its R/3 ERP software for five years.

Nichols is considering an upgrade to mySAP but fears that such a move will require the use of both the BEA middleware and NetWeaver. "I worry that when we upgrade, [Canada Post will] have to contend with both tools and my support costs will rise. I don't want to support two [products] that offer the same functionality," he said.