Requirements can be physical or descriptive (a characteristic or process, such as recycled content or sustainably managed timber), performance (standards to be met including the way of delivery that optimises social and environmental impact) or functional (the function to be fulfilled); mixing performance with functional requirements is usually the preferred approach because it lets suppliers propose the most efficient solution, and particular brands should not be specified unless unavoidable.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.