The Integration Service can distinguish empty values from null values in an XML source. You can choose to pass empty strings as null values by selecting the Treat Empty Content As NULL option in the Mapping tab of the session properties. By default, empty content is Not Null.
You can choose to omit fixed elements from the XML source definition. If the DTD or XML schema specifies a fixed or default value for an element, the value appears in the XML source definition.
You can define attributes as required, optional, or prohibited in an element tag. You can also specify fixed or default values for attributes. When a DTD or XML schema contains an attribute with a fixed or default value, the Integration Service passes the value into the pipeline even if the element tag in the instance document does not contain the attribute. If the attribute does not have a fixed or default value, the Integration Service passes a null value for the attribute. A parser error occurs when a required attribute is not present in an element or a prohibited attribute appears in the element tag. The Integration Service writes this error to the session log.