xmlns:nslt1 - nslt1 is a unique identifier refers to this service
XML namespaces are used for providing uniquely named elements and attributes in an XML document. They are defined in a W3C recommendation. An XML instance may contain element or attribute names from more than one XML vocabulary.
Now I can understand what they mean, what i don't understand is which one to use where.
Below screenshot is from a wsdl file of a simple Pega SOAP service which takes FirstName and lastName as input and generates a case ID. Both namespaces tns and nslt1 refer to the same URN and we can see that tns is used to refer type for element CreateNewWorkRequest and nslt1 is used to refer type for element CreateNewWorkResponse(refer screenshot).
Can't we use same namespace to refer types in both those elements, what is the need to have separate namespaces.