Your orginal post seemed to imply that because MS has control over the Excel XML file format, that they can control implementation of XML web services that Excel can interface with. I don't see where this is the case.

The XML schemas in question do not equal "any Excel file that uses XML". There are other ways that Excel uses XML (such as web services) that are not the XML file format that Excel can optionally generate. Now, if MS has patents on using web services from spreadsheet (or other) apps ...

Also, the licensing terms for using the Excel XML schema look quite reasonable (and royalty free) to me:

[link|http://www.microsoft.com/office/xml/faq.mspx|http://www.microsoft...fice/xml/faq.mspx]

Q. If Microsoft obtains a patent for the Office 2003 XML Reference Schemas, does that in any way affect the royalty-free license?
A. No, the license is unaffected. Under the patent license for the Office 2003 XML Reference Schemas, Microsoft offers royalty-free rights both to its issued patents and patents that may be issued in the future.

However, there is also this ...

Q. Is Microsoft committed to making any future updates to the Office 2003 XML Reference Schemas available under the same terms and conditions as the licenses offered on November 17, 2003?
A. Yes. Microsoft is committed to making updates to the Office 2003 XML Reference Schemas available under the same terms and conditions as the licenses offered on November 17, 2003. At the same time, Microsoft reserves the right to change its policy and/or the terms of the licenses with respect to future versions of Office.