There is no such thing as a second officer. The additional pilot is known as the "RP" or relief pilot and is placed on flights of a certain contractual duration. Some flights include YYC-FRA-YYC, YYZ-SCL-YYZ, FCO-YYZ & MUC-YYZ.
Ahhh. That certainly makes sense, and I appreciate the replies. I should note, that I didn't decide to call that pilot the second officer, that's how they were referred to on the announcement. Which is what twigged my interest in the first place, as I had never heard of such a position.
Michael