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RFC1034 (November 1987, Domain Names - Concepts and Facilities) discusses the architecture of the DNS, and RFC1035 (November 1987, Domain Names— Implementation and Specification) spells out the implementation details.
Recognizing that the DNS is the only truly global Internet directory but that it could never support per-resource URL resolution, RFC2168 (June 1996, Resolution of Uniform Resource Identifiers, Using the Domain Name System) proposes a hybrid approach: a DNS resource record called Naming Authority Pointer (NAPTR) that maps parts of URIs to domain names. The idea is that a URN can refer, through DNS, to a resolver that produces an address.