The name and role_name fields in the ENTITY_NAME QosPolicy (DDS Extension) have three distinct possible values: NULL, an empty string, and a non-empty string. Each of these three states are specified in XML in a different way.
To specify that the name or role_name of an entity is NULL, use the xsi:nil attribute. The xsi:nil attribute can be set to either "true" or "false". For example, to set the participant name to NULL:
<participant_name> <name xsi:nil="true"> </participant_name>
To specify the empty string, leave the XML element empty:
<participant_name> <name/> </participant_name>
To specify a non-empty string:
<participant_name> <name>"My Participant's Name"</name> </participant_name>
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