1. Introduction

   The Dynamic Delegation Discovery System (DDDS) is used to implement
   lazy binding of strings to data, in order to support dynamically
   configured delegation systems.  The DDDS functions by mapping some
   unique string to data stored within a DDDS Database by iteratively
   applying string transformation rules until a terminal condition is
   reached.

   This document describes the way in which the Domain Name System (DNS)
   is used as a data store for the Rules that allow a DDDS Application
   to function.  It does not specify any particular application or usage
   scenario.  The entire series of documents is specified in "Dynamic
   Delegation Discovery System (DDDS) Part One: The Comprehensive DDDS"
   (RFC 3401) [1].  It is very important to note that it is impossible
   to read and understand any document in that series without reading
   the related documents.

   The Naming Authority Pointer (NAPTR) DNS Resource Record (RR)
   specified here was originally produced by the URN Working Group as a
   way to encode rule-sets in DNS so that the delegated sections of a
   Uniform Resource Identifiers (URI) could be decomposed in such a way
   that they could be changed and re-delegated over time.  The result
   was a Resource Record that included a regular expression that would
   be used by a client program to rewrite a string into a domain name.

   Regular expressions were chosen for their compactness to expressivity
   ratio allowing for a great deal of information to be encoded in a
   rather small DNS packet.

   Over time this process was generalized for other Applications and
   Rule Databases.  This document defines a Rules Database absent any
   particular Application as there may be several Applications all
   taking advantage of this particular Rules Database.