Which option refers to the planning of services based on a schedule?

The correct choice is the Maintenance Plan. A Maintenance Plan is specifically designed to schedule and plan services systematically over time. It outlines the frequency, type, and timing of maintenance activities needed to ensure that equipment or machinery operates efficiently and effectively. This proactive approach is significant in industries where equipment maintenance is critical to operations.

By utilizing a Maintenance Plan, businesses can avoid unexpected breakdowns and reduce downtime, all while managing resources and costs effectively. This option highlights the importance of strategic scheduling in service management, making it critical for ensuring compliance and optimizing service delivery.

In contrast, other options like Service Order, Service Contract, and Service Request focus more on the transactional or contractual aspects of service management rather than establishing a planned schedule for repeated services. Service Orders pertain to specific tasks issued for service execution, Service Contracts define the terms of service between parties, and Service Requests generally refer to individual requests for service or support.