"xsf2" namespace issue with K2 and infopath 2007

Recently when trying to upgrade an InfoPath form from 2003 and 2007, then integrate it with K2 workflow, the error "Namespace prefix 'xsf2' is not defined" popped up.

Thanks for the hints from Infopath Edit The Manifest (by SLADESCROSS), this problem is easy to fix:

1. Change the “.xsn” file to “.cab” file;

2.  Uncompress it to a separate folder;

3.  Edit the “.xsf” file through notepad or any other plain text editor;

4.  Add the attribute below to the root node “xsf:xDocumentClass” (after the “xmlns:xsf” attribute, to keep consistent with normal InfoPath 2007 form), then save it.

xmlns:xsf2=http://schemas.microsoft.com/office/infopath/2006/solutionDefinition/extensions

5.  Open the infopath 2007 program in design mode, then open that modified “.xsf” file

6.  Save the form to a new “.xsn” file

After that, we can integrate the new form into K2   :-)

Update: Using an InfoPath form from a K2.net 2003 process in BlackPearl  mentioned similar solution to upgrade K2.net 2003 InfoPath form.