The Series Transfer Pattern (STP)
draft-bormann-t2trg-stp-01

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Network Working Group                                         C. Bormann
Internet-Draft                                   Universitaet Bremen TZI
Intended status: Informational                                 K. Hartke
Expires: January 1, 2019                                        Ericsson
                                                           June 30, 2018

                   The Series Transfer Pattern (STP)
                       draft-bormann-t2trg-stp-01

Abstract

   Many applications make use of Series of data items, i.e., an array of
   data items where new items can be added over time.  Where such Series
   are to be made available using REST protocols such as CoAP or HTTP,
   the Series has to be mapped into a structure of one or more resources
   and a protocol for a client to obtain the Series and to learn about
   new items.

   Various protocols have been standardized that make Series-shaped data
   available, with rather different properties and objectives.  The
   present document is an attempt to extract a common underlying pattern
   and to define media types and an access scheme that can be used right
   away for further protocols that provide Series-shaped data.

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Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Objectives  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  A REST Series Transfer Pattern (STP)  . . . . . . . . . . . .   4
     3.1.  Basic collections . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Pagination and Observing linked lists . . . . . . . . . .   5
     3.3.  The "cursor" pattern  . . . . . . . . . . . . . . . . . .   7
   4.  IANA considerations . . . . . . . . . . . . . . . . . . . . .   8
   5.  Security considerations . . . . . . . . . . . . . . . . . . .   9
   6.  Informative References  . . . . . . . . . . . . . . . . . . .   9
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   (TO DO: Insert an extended form of the abstract first here, expanding
   the reference to [RFC7230] and [RFC7252] in the process.)

   Examples for protocols that provide Series-shaped data are:

   o  The Atom Syndication Format [RFC4287] defines _feeds_ as Series of
      _entries_ (links plus some metadata, which can often be much of
      the content of an entry), where a feed is represented by a
      collection resource that contains just a small number of the most
      recent entries.  By polling a feed, a client can contain a fresh
      view of the Series, with a focus on recent items.  If the client
      does not poll often enough, it will _miss_ items.

   o  Messaging protocols such as XMPP or SIMPLE transfer series of what
      is often called "Instant Messages".  A publish/subscribe mechanism
      allows a client to select sequences of messages that it is
      interested in.

   o  Mail servers that provide interactive access to stored messages
      present a Series to their clients.  Obviously, loss of messages is
      frowned upon.

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   o  CoAP Observe allows a client to observe a resource as it changes;
      the client can collect the changes into a Series.  Observe is
      focused on eventual consistency: a fresher data items simply
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