Availability asks what proportion of a stated period the product is usable. A measure relates uptime to the period, with the service window and the treatment of maintenance stated. Availability is a ratio with a political denominator. Planned maintenance, partial degradation and dependency outages can each be counted in or out, and the choice changes the number. The measure should state the service window, the monitoring points and the treatment of each exclusion. A monitor that checks one endpoint measures that endpoint, not the product. Availability also depends on the dependencies the product does not control, and the measure should say whether they are in scope.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.