Optional numeric fields in InfoPath

In an earlier post I wrote about optional and non-required elements in XSD schemas, especially date and decimal (double) elements, and how InfoPath deals with such elements. I was annoyed that I could not get them to be optional when included in the InfoPath main data source (schema scope).

Today I took a closer look at this problem, and instead of starting with the service contract (WSCF) and creating an InfoPath form based on the generated web service, I designed a new form from scratch by building the data source (XSD schema) using InfoPath. And, lo and behold, the decimal fields added manually to the data source are by default optional! The 'Cannot be blank' checkbox is enabled and unchecked!

I extracted the form files and inspected the XSD schema, and the element had both minOccurs="0" and nillable="true". Just as I had defined the decimal elements in the XSD schemas used in my service contract. So, why the different behavior ?

To find out why, I opened one of the InfoPath forms made by connecting to a WSCF web service and then extracted the form files. When I inspected the schemas, the nillable="true" was not in the XSD schema induced by InfoPath. By adding the attribute manually to the schema and then opening the form definition file (.XSF) with InfoPath, the problem was solved and my decimal fields are now truly optional in InfoPath. Note that this fix will be gone as soon as you re-induce the data source schemas.

Is this a bug with regards to nillable in the generated WSDL, web service or just the way it is ? Or, more likely, a weakness in InfoPath ? To be continued...