Hope you have already found way to do this.
To answer your query, for mapping, Event ID and category are required to create QID. so in this case, you can choose fields which are unique let's say event category = field which shows logtype and event ID would be some other unique field.
once you parse , these fields will be used to create QID
Hope this helps!
------------------------------
[Ashish] [Khandewale] [Security Consultant]
[SIOC]
[IBM Canada]
------------------------------