[en] The Cherenkov Telescope Array (CTA) is the next-generation atmospheric Cherenkov gamma-ray observatory. The Observation Execution System (OES) team within the CTA project is designing and prototyping the software to execute the observations and to handle the acquisition of scientific data at GB/s rates. In this contribution we show the OES system as it is being designed using the Unified Modeling Language (UML) and Systems Modeling (SysML) formalisms. In addition, we present the status of the associated prototyping activities. (paper)