Verified properties express supply chain controls that do not fit a level and may be placed in a VSA's verifiedLevels when the issuer finds their requirements met. SLSA_SOURCE_TWO_PARTY_REVIEWED may be issued only where the Source track rules on review by two parties are met, at any Source level where the SCS can make that claim. SLSA_BUILD_REPRODUCED may be issued only when at least two build platforms, run independently of each other and both trusted by the VSA issuer, have produced build provenance for the artifact.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.