1.1 Purpose: The Scheduling and Commanding Messages (SCM) specifies a standard format for observing system commanding and scheduling. This document aims to ease the planning and operation processes and to reduce the effors from researchers that use several different observing systems and/or simulation software products. The SCM establishes a common language for exchanging information on planning, scheduling, and executing observations of celestial objects. In the end this will: a) Facilitate interoperability and enable consistent warning between data originators who supply celestial observations and the entities or researchers who use it; and b) Facilitate the automation of observation processes. 1.2 Applicability: The SCM is applicable to ground-based activities related to the planning, scheduling, and execution of the observations of celestial objects. It is used by planning software, scheduling software, telescope commanding software. It is applicable for optical telescopes.