Codeshare notation format?
 

I've seen people notate codeshares using asterisks, e.g. AA*BA or AA*IB, but even though I've searched via Google and the forum search, and consulted the glossary, I haven't found any explanation as to which order the notation typically goes.

Is the usual notation (marketing carrier)*(operating carrier)? Is this even a thing that people use, or is this just a niche thing that people don't actually use or would understand?