Why

We've started to reference to sandwich transactions since the introduction of CAP-33 and CAP-18. We talked about the "sandwich approach" in CAP-33, and we also talked about the authorization sandwich in the control asset access section in our new doc.

Recently one of our partners has expressed the difficulty about communicating the use of sandwich transactions through approval_criteria in the currencies section of SEP-1.

Having a formal definition of sandwich transactions would facilitate such communications.