Policy Decision Point (PDP)
The component that evaluates a policy against a request and returns a decision — permit, deny, or something more nuanced — without itself blocking or allowing anything.
aka: PDP
Splitting decision from enforcement — the PDP decides, the PEP acts — is the payoff of XACML’s four-component split: the same PDP can serve many PEPs across an architecture, policies can be updated centrally without touching every enforcement point, and Zero Trust’s Trust Algorithm plays exactly this PDP role in NIST’s model.