Help with test SOAP Web Service

Hi all

i'm try to test a SOAP Web Service; in the Wsdl i have some element with minOccurs="0" and other minOccurs="1" . I'm expecting that if the element with minOccurs="1" is not filled , SOAP Ui tell me that the element is mandatory, instaed the Web Service runs normally.

Can you help me to understand where am i wrong ?

thanks