Independent Submission                                       M. Basaglia
Request for Comments: 9402
Category: Informational                                      J. Bernards
ISSN: 2070-1721
                                                                J. Maas
                                                           1 April 2023


                           Concat Notation

Abstract

  This document defines the Concat notation: a text-based language used
  to describe pictures and videos whose subject includes cats,
  containers, and their interactions.

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 candidates for any level of Internet Standard;
  see Section 2 of RFC 7841.

  Information about the current status of this document, any errata,
  and how to provide feedback on it may be obtained at
  https://www.rfc-editor.org/info/rfc9402.

Copyright Notice

  Copyright (c) 2023 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
  (https://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.

Table of Contents

  1.  Introduction
    1.1.  Conventions Used in This Document
  2.  Definition
    2.1.  Terminology
    2.2.  Grammar
  3.  Elements
    3.1.  Subjects
      3.1.1.  Cats
      3.1.2.  Partial Cats
      3.1.3.  Other Animals
      3.1.4.  Balls of Yarn
    3.2.  Containers
    3.3.  Positioning
      3.3.1.  Horizontal Position
      3.3.2.  Vertical Position
      3.3.3.  Multiple Repeated Objects
    3.4.  Changes over Time
      3.4.1.  Disambiguation
  4.  Internationalization Considerations
  5.  Security Considerations
  6.  IANA Considerations
  7.  Normative References
  Appendix A.  Examples
  Authors' Addresses

1.  Introduction

  Cat pictures and videos are often shared across the Internet.  Many
  of these files display feline subjects interacting with boxes and
  other containers.

  Since there is currently no compact notation for describing such
  media, this document details a standard notation to describe the
  position and interaction of cats, containers, and related subjects
  pictured in these images.

  The notation language described in this document is text-based and
  limits itself to the US-ASCII character encoding [RFC0020], allowing
  the transfer of cat-related materials in environments with restricted
  capabilities.

1.1.  Conventions Used in This Document

  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
  "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
  "OPTIONAL" in this document are to be interpreted as described in
  BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
  capitals, as shown here.

2.  Definition

2.1.  Terminology

  This document uses specific terms to refer to items being depicted by
  the notation described herein.

  To avoid ambiguity, such terms are defined as follows:

  Subject:  The term "subject" is used in this document to refer to the
     object that is the focus in the media to be annotated.  This
     usually is an animate object, specifically a cat.  An annotation
     can have multiple subjects interacting in various ways.

  Cat:  A cat is a special kind of subject of feline origin.  This
     document will assume a house cat is present in the source media;
     however, other felines are also acceptable.

  Container:  The term "container" is used to refer to inanimate
     objects inside of which one or more subjects can be located.  Most
     commonly, this will be a cardboard box; however, a variety of
     containers can be used.

2.2.  Grammar

  The grammar is defined using the ABNF notation [RFC5234].

  SEQUENCE  =  POSITION / POSITION "=>" SEQUENCE
  POSITION  =  ADJACENT
  ADJACENT  =  OVER / ADJACENT "+" OVER
  OVER      =  MULTIPLE / MULTIPLE "/" POSITION
  MULTIPLE  =  CONCAT / NUMBER [ "*" ] MULTIPLE / NUMBER "/" MULTIPLE
  CONCAT    =  SUBJECT [ NUMBER ] / [ PARTIAL ] CONTAINER [ PARTIAL ]
  CONTAINER =  "[" OPT-POS "]" / "(" OPT-POS ")"
  CONTAINER =/ "{" OPT-POS "}" / "<" OPT-POS ">"
  OPT-POS   =  [ POSITION ]
  SUBJECT   =  CAT / 1*ALPHA / "@"
  CAT       =  "cat" / PARTIAL
  PARTIAL   =  "c" / "a" / "t" / "ca" / "at"
  ALPHA     =   %x41-5A / %x61-7A
  NUMBER    =  1*DIGIT
  DIGIT     =  "0" / "1" / "2" / "3" / "4"
  DIGIT     =/ "5" / "6" / "7" / "8" / "9"

3.  Elements

3.1.  Subjects

3.1.1.  Cats

  The standard notation for a cat is the word cat.

3.1.2.  Partial Cats

  When referencing cats partly inside a container, the annotation MUST
  contain the full cat mark adequately split inside and outside the
  container.

  If a cat is only partly visible in the frame of the picture or video,
  the annotation MAY only reference the visible portion of the cat.

  The partial cat notations are as follows:

  c:  marks the head of the cat.

  a:  marks the body of the cat.

  t:  marks the tail of the cat.

  ca:  marks the head and body of the cat.

  at:  marks the body and tail of the cat.

  The annotation for a partial cat SHOULD use the terms mentioned above
  that best describe the portion of the cat that is being referenced.

3.1.3.  Other Animals

  Other animals or animate objects SHOULD be represented with a
  suitable word describing the species of such animal.  The cat-
  specific words described in this document MUST NOT be used for non-
  feline subjects.

3.1.4.  Balls of Yarn

  Balls of yarn SHOULD be represented with @.

3.2.  Containers

  When a cat or other subject is inside a container, the container
  notation MUST be used.  Such notation is denoted by its subject being
  between brackets.  The type of bracket depends on the shape of the
  container as follows:

  *  Square brackets represent boxes or other containers with a
     rectangular opening.

  *  Parentheses represent containers with a round opening or shape.

  *  Curly braces SHALL be used to represent soft containers without a
     fixed shape.

  Additionally, angle brackets MAY be used to group subjects outside a
  container.  Such annotations MUST NOT contain partial cats.

3.3.  Positioning

  The Concat notation only gives information about the general layout
  of subjects and containers, but it does make a distinction between
  horizontal and vertical positions.

  The order of positional operands SHOULD follow the order in which
  they appear from left to right in the source media.

3.3.1.  Horizontal Position

  The + operator is used to represent subjects or containers next to
  each other.

3.3.2.  Vertical Position

  When a subject is above or on top of another, the operator / MUST be
  used.

3.3.3.  Multiple Repeated Objects

  When multiple objects or configurations are repeated, the shorthand
  notation MAY be used.

  Horizontal positioning is denoted by a number followed by an optional
  * and the annotation to be repeated.

  Similarly, for vertical positioning, repeated objects are denoted by
  a number followed by / and the annotation to be repeated.

  When using such a shorthand, the number of repetitions MUST be a
  positive integer.

3.4.  Changes over Time

  In the case of videos or other animations, a proper Concat notation
  SHOULD make use of the state change operator (=>) to mark significant
  changes in the cat position and major interactions.

3.4.1.  Disambiguation

  Subject tokens MAY be followed by an integer identifier to
  distinguish specific cats, balls of yarn, or other subjects.  An
  annotation containing such numeric disambiguations MUST contain such
  disambiguations for all cats and balls of yarn.

  Since a specific subject can only appear once in a static image,
  disambiguation identifiers SHOULD be used only on annotations showing
  state changes.

4.  Internationalization Considerations

  The word cat is in English and is provided to allow transfer of
  Concat notations using only the US-ASCII character encoding
  [RFC0020].

  Users of other languages MAY extend the alphabet and use their
  localized words for cat and other animals.

  Non-standard words for cats SHOULD NOT be used unless all parties
  involved in the production and consumption of the Concat notation
  have agreed upon a character encoding and a language prior to the
  transmission of the annotation.

5.  Security Considerations

  A cat might find themselves in a container smaller than the perceived
  volume of the cat.  While this might seem to be a dangerous
  situation, it's actually a natural occurrence when the cat is in its
  liquid form.

  Cats might chew on the cardboard of the box containing them.  To
  mitigate this attack, we recommend having multiple boxes to put the
  cats into.

6.  IANA Considerations

  This document has no IANA actions.

7.  Normative References

  [RFC0020]  Cerf, V., "ASCII format for network interchange", STD 80,
             RFC 20, DOI 10.17487/RFC0020, October 1969,
             <https://www.rfc-editor.org/info/rfc20>.

  [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119,
             DOI 10.17487/RFC2119, March 1997,
             <https://www.rfc-editor.org/info/rfc2119>.

  [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
             Specifications: ABNF", STD 68, RFC 5234,
             DOI 10.17487/RFC5234, January 2008,
             <https://www.rfc-editor.org/info/rfc5234>.

  [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
             2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
             May 2017, <https://www.rfc-editor.org/info/rfc8174>.

Appendix A.  Examples

  This appendix provides some examples of the Concat notation.

  [cat]

                         Figure 1: A Cat in a Box

  [cat] + cat

           Figure 2: A Cat in a Box Next to a Cat Not in a Box

  cat / [cat]

            Figure 3: A Cat over a Box Containing Another Cat

  [c]at

                Figure 4: A Cat with Its Head inside a Box

  3 * cat

                      Figure 5: 3 Cats Side by Side

  3 / cat

                  Figure 6: 3 Cats on Top of Each Other

  cat + cat / [cat]

     Figure 7: A Cat Standing Next to a Box That Has a Cat on Top and
                               inside of It

  <cat + cat> / [cat]

    Figure 8: Two Cats Standing on a Box with Another Cat inside of It

  cat1 + [cat2] => cat2 + [cat1]

        Figure 9: A Cat inside a Box and a Cat outside Swap Places

Authors' Addresses

  Mattia Basaglia
  Email: [email protected]
  URI:   https://dragon.best/


  Joep Bernards
  Email: [email protected]


  Joost Maas
  Email: [email protected]

You are viewing proxied material from gopher.fnord.one. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.