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Updates:
Independent Submission I. Nazar
Request for Comments: 7168 1 April 2014
Updates: 2324
Category: Informational
ISSN: 2070-1721
The Hyper Text Coffee Pot Control Protocol
for Tea Efflux Appliances (HTCPCP-TEA)
Abstract
The Hyper Text Coffee Pot Control Protocol (HTCPCP) specification
does not allow for the brewing of tea, in all its variety and
complexity. This paper outlines an extension to HTCPCP to allow for
pots to provide networked tea-brewing facilities.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This is a contribution to the RFC Series, independently of any other
RFC stream. The RFC Editor has chosen to publish this document at
its discretion and makes no statement about its value for
implementation or deployment. Documents approved for publication by
the RFC Editor are not a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7168.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document.
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RFC 7168 HTCPCP-TEA 1 April 2014
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. HTCPCP-TEA Protocol Additions . . . . . . . . . . . . . . . . . 3
2.1. BREW and POST Methods . . . . . . . . . . . . . . . . . . . 3
2.1.1. The "/" URI . . . . . . . . . . . . . . . . . . . . . . 3
2.1.2. Variety-Specific URIs . . . . . . . . . . . . . . . . . 4
2.2. Modified Header Fields . . . . . . . . . . . . . . . . . . 4
2.2.1. The Accept-Additions Header Field . . . . . . . . . . . 4
2.3. Response Codes . . . . . . . . . . . . . . . . . . . . . . 5
2.3.1. 300 Multiple Options . . . . . . . . . . . . . . . . . 5
2.3.2. 403 Forbidden . . . . . . . . . . . . . . . . . . . . . 5
2.3.3. 418 I'm a Teapot . . . . . . . . . . . . . . . . . . . 5
3. The "message/teapot" Media Type . . . . . . . . . . . . . . . . 6
4. Environmental Considerations . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . . 7
1. Introduction
As noted in the Hyper Text Coffee Pot Control Protocol [HTCPCP],
coffee is renowned worldwide as an artfully brewed caffeinated
beverage, but coffee shares this quality with many other varied
preparations based on the filtration of plant material. Foremost,
among these are the category of brews based on the straining of water
through prepared leaves from a tea tree: the lineage and history of
the tea genus will not be recounted as part of this paper, but
evidence shows that the production of tea existed many thousands of
years ago.
The deficiency of HTCPCP in addressing the networked production of
such a venerable beverage as tea is noteworthy: indeed, the only
provision given for networked teapots is that they not respond to
requests for the production of coffee, which, while eminently
reasonable, does not allow for communication with the teapot for its
intended purpose.
This paper specifies an extension to HTCPCP to allow communication
with networked tea production devices and teapots. The additions to
the protocol specified herein permit the requests and responses
necessary to control all devices capable of making, arguably, the
most popular caffeinated hot beverage.
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1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [KEYWORDS].
2. HTCPCP-TEA Protocol Additions
The TEA extension to HTCPCP adapts the operation of certain HTCPCP
methods.
2.1. BREW and POST Methods
Control of a TEA-capable pot is performed, as described in the base
HTCPCP specification, through the sending of BREW requests. POST
requests are treated equivalently, but they remain deprecated. Tea
production differs from coffee, however, in that a choice of teas is
often provided for client selection before the tea is brewed. To
this end, a TEA-capable pot that receives a BREW message of content
type "message/teapot" MUST respond in accordance with the URI
requested, as below.
2.1.1. The "/" URI
For the URI "/", brewing will not commence. Instead, an Alternates
header as defined in RFC 2295 [RFC2295] MUST be sent, with the
available tea bags and/or leaf varieties as entries. An example of
such a response is as follows:
Alternates: {"/darjeeling" {type message/teapot}},
{"/earl-grey" {type message/teapot}},
{"/peppermint" {type message/teapot}}
The following example demonstrates the possibility of
interoperability of a TEA-capable pot that also complies with the
base HTCPCP specification:
Alternates: {"/" {type message/coffeepot}},
{"/pot-0/darjeeling" {type message/teapot}},
{"/pot-0/earl-grey" {type message/teapot}},
{"/pot-1/peppermint" {type message/teapot}}
TEA-capable HTCPCP clients MUST check the contents of the Alternates
header returned by a BREW request, and provide a specific URI for
subsequent requests of the "message/teapot" type.
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A request to the "/" URI with a Content-Type header of
"message/coffeepot" SHOULD also be responded to with an Alternates
header in the above format, to allow TEA-capable clients the
opportunity to present the selection of teas to the user if inferior
caffeinated beverages have initially been requested.
2.1.2. Variety-Specific URIs
TEA-capable pots follow the base HTCPCP specification when presented
with a BREW request for a specific variety of tea. Pots SHOULD
follow the recommendations for brewing strength given by each
variety, and stop brewing when this strength is reached; it is
suggested that the strength be measured by detection of the opacity
of the beverage currently under brew by the pot.
TEA-capable clients SHOULD indicate the end of brewing by sending a
BREW request with an entity body containing "stop"; the pot MAY
continue brewing beyond the recommended strength until this is
received. If the "stop" request is not sent by the client, this may
result in a state inversion in the proportion of tea to water in the
brewing pot, which may be reported by some pots as a negative
strength.
If a BREW command with an entity body containing "stop" is received
before the recommended strength is achieved, the pot MUST abort
brewing and serve the resultant beverage at lesser strength. Finding
the preferred strength of beverage when using this override is a
function of the time between the TEA-capable pot receiving a "start"
request and the subsequent "stop". Clients SHOULD be prepared to
make multiple attempts to reach the preferred strength.
2.2. Modified Header Fields
HTCPCP-TEA modifies the definition of one header field from the base
HTCPCP specification.
2.2.1. The Accept-Additions Header Field
It has been observed that some users of blended teas have an
occasional preference for teas brewed as an emulsion of cane sugar
with hints of water. To allow for this circumstance, the Accept-
Additions header field defined in the base HTCPCP specification is
updated to allow the following options:
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addition-type = ( "*"
| milk-type
| syrup-type
| sweetener-type
| spice-type
| alcohol-type
| sugar-type
) *( ";" parameter )
sugar-type = ( "Sugar" | "Xylitol" | "Stevia" )
Implementers should be aware that excessive use of the Sugar addition
may cause the BREW request to exceed the segment size allowed by the
transport layer, causing fragmentation and a delay in brewing.
2.3. Response Codes
HTCPCP-TEA makes use of normal HTTP error codes and those defined in
the base HTCPCP specification.
2.3.1. 300 Multiple Options
A BREW request to the "/" URI, as defined in Section 2.1.1, will
return an Alternates header indicating the URIs of the available
varieties of tea to brew. It is RECOMMENDED that this response be
served with a status code of 300, to indicate that brewing has not
commenced and further options must be chosen by the client.
2.3.2. 403 Forbidden
Services that implement the Accept-Additions header field MAY return
a 403 status code for a BREW request of a given variety of tea, if
the service deems the combination of additions requested to be
contrary to the sensibilities of a consensus of drinkers regarding
the variety in question.
A method of garnering and collating consensus indicators of the most
viable combinations of additions for each variety to be served is
outside the scope of this document.
2.3.3. 418 I'm a Teapot
TEA-capable pots that are not provisioned to brew coffee may return
either a status code of 503, indicating temporary unavailability of
coffee, or a code of 418 as defined in the base HTCPCP specification
to denote a more permanent indication that the pot is a teapot.
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3. The "message/teapot" Media Type
To distinguish messages destined for TEA-capable HTCPCP services from
pots compliant with the base HTCPCP specification, a new MIME media
type is defined by this document. The Content-Type header of a POST
or BREW request sent to a TEA-capable pot MUST be "message/teapot" if
tea is to be requested.
4. Environmental Considerations
As noted in Section 2.1, a BREW request with a Content-Type header
field of "message/teapot" to a TEA-capable pot will result in an
Alternates header being sent with the response, and a pot will not be
brewed. However, if the BREW request has a Content-Type of
"message/coffeepot", and the pot is capable of brewing coffee, the
service's behavior will fall back to the base HTCPCP specification
and a pot will be brewed.
If the entity returned by the server when brewing commences contains
a TEA-compliant Alternates header indicating "message/coffeepot" and
the client does not want coffee, the client SHOULD then send a BREW
request with an entity body containing "stop". This will result in
wasted coffee; whether this is regarded as a bad thing is user-
defined.
Such waste can be prevented by TEA-capable clients, by first
requesting a BREW of type "message/teapot" and then allowing
selection of an available beverage.
5. Security Considerations
As with the base HTCPCP specification, most TEA-capable pots are
expected to heat water through the use of electric elements, and as
such will not be in proximity to fire. Therefore, no firewalls are
necessary for communication with these pots to proceed.
This extension does support communication with fired pots, however,
which may require heat retention and control policies. Care should
be taken so that coal-fired pots and electrically heated kettles are
not connected to the same network, to prevent pots from referring to
any kettles on the network as darkened or otherwise smoke driven.
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6. Acknowledgements
This extension to the HTCPCP specification would not be possible
without the base specification, and research on networked beverage
production leading up thereto. In that vein, the author wishes to
acknowledge the sterling work of Larry Masinter in the development of
the leading protocol for coffee pot communication.
Many thanks also to Kevin Waterson and Pete Davis, for providing
guidance and suggestions during the drafting of this document.
7. References
7.1. Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. Informative References
[HTCPCP] Masinter, L., "Hyper Text Coffee Pot Control Protocol
(HTCPCP/1.0)", RFC 2324, April 1 1998.
[RFC2295] Holtman, K. and A. Mutz, "Transparent Content Negotiation
in HTTP", RFC 2295, March 1998.
Author's Address
Imran Nazar
deviantART Inc.
7095 Hollywood Blvd
Hollywood, CA 90028
EMail: inazar@deviantart.com
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