Field Limitations
You might encounter the following issues when working with Microsoft Office InfoPath:
IS document types generated from an InfoPath XSD may contain field names that
webMethods Broker will not propagate to non IS-clients.
InfoPath template fields intended to be mandatory are imported into an IS document type with the fields shown as optional. This applies to InfoPath template fields with the "Cannot be blank" property selected. When InfoPath renders the form into an XML Schema, these fields are shown as optional, which is how they are treated when they are imported into an IS document type.
This is caused by the way InfoPath handles attributes. Attribute elements are optional by default; in this case, the "use" attribute for the field in question should be set to "required." If this value is not specified, then the default value is "optional" and it is imported as such.
For more information, you can refer to these sources: