Faultlessness asks how rarely the product fails in operation or in test. A measure relates failures to the exposure that produced them. A failure count without exposure is not comparable. Exposure can be time, transactions, users or sessions, and the right unit depends on the product. The draft separates faultlessness from availability because a product can be unavailable for reasons other than failure, such as planned maintenance, and can fail without becoming unavailable if it recovers. The measure should use a written failure definition and a severity scale, and it should name the window.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.