Change XSD Type of a ABAP Webservice for a Function Module

Hello.

i wrote a FM for uploading GTS SPL content to SAP. From this FM i generated

a Enterprise Service / Service Definition and published it via SOAMANAGER.

So everything works fine.

But now i want to change the field "SLL_SPL_DOB_TO" to a nillable field. Meaning

that the date in this field can be empty.

For the moment it must not be null. But in some cases the date field is empty and

the webservice doesnt not work for empty fields.

I tried to change some attributes within the structure, but the fields are grayed out.

Below you can see my implementation. I want to set the element SLL_SPL_DOB_TO to

allow empty values.

In the SAP Standard Webservice (but it is a XI service) there are option to set

the required information.

Is there a way to set the information ? Or how the information for required or not

required fields are set and mapped to XSD Types and their options ?

Thanks a lot for your help.

BR,

Sebastian