Error message structure explanation

Hi,

Our client wants to save the relevant error from OTM's transmission report (see example below) in SAP. Problem is that the message text is very long and they want to put it in to a 200 character field. We would like to have a more user understandable version like "THE FOREIGN KEY ELEMENT LocationRef.LocationGid WITH VALUE TMS.3005XXX COULD NOT BE FOUND IN TABLE LOCATION COLUMN location_gid"

Could someone explain how OTM generates the element <otm:IMessageText>, so we can find some business logic to get the relevant information out in less than 200 characters?

Any suggestions and ideas appreciated!