The Protocol versus Document Points of View in Computer Protocols
RFC 3930

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Network Working Group                                    D. Eastlake 3rd
Request for Comments: 3930                         Motorola Laboratories
Category: Informational                                     October 2004

   The Protocol versus Document Points of View in Computer Protocols

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   This document contrasts two points of view: the "document" point of
   view, where digital objects of interest are like pieces of paper
   written and viewed by people, and the "protocol" point of view where
   objects of interest are composite dynamic network messages.  Although
   each point of view has a place, adherence to a document point of view
   can be damaging to protocol design.  By understanding both points of
   view, conflicts between them may be clarified and reduced.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Points of View . . . . . . . . . . . . . . . . . . . . . . . .  2
       2.1.  The Basic Points of View . . . . . . . . . . . . . . . .  3
       2.2.  Questions of Meaning . . . . . . . . . . . . . . . . . .  3
             2.2.1.  Core Meaning . . . . . . . . . . . . . . . . . .  3
             2.2.2.  Adjunct Meaning. . . . . . . . . . . . . . . . .  4
       2.3.  Processing Models. . . . . . . . . . . . . . . . . . . .  5
             2.3.1.  Amount of Processing . . . . . . . . . . . . . .  5
             2.3.2.  Granularity of Processing. . . . . . . . . . . .  5
             2.3.3.  Extensibility of Processing. . . . . . . . . . .  6
       2.4.  Security and Canonicalization. . . . . . . . . . . . . .  6
             2.4.1.  Canonicalization . . . . . . . . . . . . . . . .  6
             2.4.2.  Digital Authentication . . . . . . . . . . . . .  8
             2.4.3.  Canonicalization and Digital Authentication. . .  8
             2.4.4.  Encryption . . . . . . . . . . . . . . . . . . .  9
       2.5.  Unique Internal Labels . . . . . . . . . . . . . . . . . 10
   3.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
   4.  Resolution of the Points of View . . . . . . . . . . . . . . . 11

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RFC 3930          Protocol versus Document Viewpoints   October 2004

   5.  Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 12
   6.  Security Considerations. . . . . . . . . . . . . . . . . . . . 12
   Informative References . . . . . . . . . . . . . . . . . . . . . . 12
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14
   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 15

1.  Introduction

   This document contrasts: the "document" point of view, where digital
   objects of interest are thought of as pieces of paper written and
   viewed by people, and the "protocol" point of view, where objects of
   interest are composite dynamic network messages.  Those accustomed to
   one point of view frequently have great difficulty appreciating the
   other:  Even after they understand it, they almost always start by
   considering things from their accustomed point of view, assume that
   most of the universe of interest is best viewed from their
   perspective, and commonly slip back into thinking about things
   entirely from that point of view.  Although each point of view has a
   place, adherence to a document point of view can be damaging to
   protocol design.  By understanding both points of view, conflicts
   between them may be clarified and reduced.

   Much of the IETF's traditional work has concerned low level binary
   protocol constructs.  These are almost always viewed from the
   protocol point of view.  But as higher level application constructs
   and syntaxes are involved in the IETF and other standards processes,
   difficulties can arise due to participants who have the document
   point of view.  These two different points of view defined and
   explored in section 2 below.

   Section 3 gives some examples.  Section 4 tries to synthesize the
   views and give general design advice in areas that can reasonably be
   viewed either way.

2.  Points of View

   The following subsections contrast the document and protocol points
   of view.  Each viewpoint is EXAGGERATED for effect.

   The document point of view is indicated in paragraphs headed "DOCUM",
   and the protocol point of view is indicated in paragraphs headed
   "PROTO".

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RFC 3930          Protocol versus Document Viewpoints   October 2004

2.1.  The Basic Points of View

   DOCUM: What is important are complete (digital) documents, analogous
      to pieces of paper, viewed by people.  A major concern is to be