Network Working Group                                  N. Brownlee (Ed.)
Internet-Draft                                The University of Auckland
Intended status: Informational                                       IAB
Expires: August 2, 2014
                                                        January 29, 2014


                   SVG Drawings for RFCs: SVG 1.2 RFC
                       draft-brownlee-svg-rfc-00

Abstract

   This document specifies SVG 1.2 RFC - an SVG profile for use in
   diagrams that may appear in RFCs - and considers some of the issues
   concerning the creation and use of such diagrams.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  SVG 1.2 RFC: An SVG profile for RFCs  . . . . . . . . . . . .   3
   3.  How to create SVG drawings  . . . . . . . . . . . . . . . . .   4
   4.  Meta-language for diagrams common in RFCs . . . . . . . . . .   4
     4.1.  State Diagrams  . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Sequence Digrgams . . . . . . . . . . . . . . . . . . . .   4
     4.3.  Packet Layout Diarrams  . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   7.  Revision History [RFC Editor please delete] . . . . . . . . .   4
   8.  Appendix: Elements and attributes allowed in SVG 1.2 RFC  . .   5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Over the last two years the RFC Editor has worked with the Internet
   community to develop specifications for changes in the format of
   RFCs.  An outline of the resulting specifications was published as
   [RFC6949] in May 2013.  Since then a Design Team has been working
   with the RFC Editor to flesh out those specifications.  One aspect of
   the changes is to allow line drawings in RFCs; [RFC6949] says

      "Graphics may include ASCII art and a more complex form to be
      defined, such as SVG line art [SVG].  Color and grayscale will not
      be accepted.  RFCs must correctly display in monochromatic black-
      and-white to allow for monochrome displays, black-and- white
      printing, and support for visual disabilities."

   SVG (Scalable Vector Graphics) has been developed by W3C, the World
   Wide Web Consortium; its current standard is SVG 1.1 Full
   [W3C.REC-SVG11-20110816].  This document defines SVG 1.2 RFC, an SVG
   profile (i.e. a subset of SVG) that is suitable for RFC line
   drawings.

   Note that in RFCs, the text provides normative descriptions of
   protocols, systems, etc.  Diagrams may be used to help explain
   concepts more clearly, but they are informative, not normative.

   RFCs will be published in new formats such as http, pdf and epub, as
   well as the traditional text format.  As well as providing diagrams
   in SVG, authors may also provide ASCII art versions for use in the
   text version.





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2.  SVG 1.2 RFC: An SVG profile for RFCs

   As a starting point for SVG 1.2 RFC, the Design Team decided to use
   SVG 1.2 Tiny [W3C.REC-SVGTiny12-20081222].  SVG 1.2 Tiny is an SVG
   subset intended to be implemented on small, mobile devices such as
   cellphones and smartphones.  That should allow RFCs to be rendered
   well on such devices, especially those that have small screens.
   However, RFCs are self-contained documents that do not change once
   they are published.  The use of SVG drawings in RFCs is intended to
   allow authors to create drawings that are simple to produce, and
   easier to understand than our traditional 'ASCII Art' ones.  In
   short, we are also trying to improve access to the content in RFCs,
   so SVG drawings need to be kept as simple as possible.

   SVG can provide a complete User Interface, but within RFCs, all we
   need are simple diagrams that do not change once the RFC is
   published.  Therefore, SVG RFC does not allow anything from the
   following sections in SVG Tiny 1.2 [W3C.REC-SVGTiny12-20081222]:

   12  Multimedia
   13  Interactivity
   15  Scripting
   16  Animation
   18  Metadata
   19  Extensibility

   Considering the other sections in SVG Tiny 1.2
   [W3C.REC-SVGTiny12-20081222]:

    9 Basic Shapes
   10 Text
        Everything in these sections is allowed in SVG 1.2 RFC.

   11 Painting: Filling, Stroking, Colors and Paint Servers
        Anything relating to 'color' is not allowed in SVG 1.2 RFC,
        everything else is allowed.

   14 Linking
        Linking is allowed in SVG 1.2 RFC, but only to components within
        the same RFC.
        [Suggestion: SVG Tiny 1.2 allows internationalized IRIs in
        references.  We could allow links to any document, but limit
        such links to be ASCII only.  That should not cause
        problems,since one can just use the URI form of any IRI.]

   17 Fonts
        SVG 1.2 RFC only allows 'serif', 'sans-serif' and 'monospace'
        generic font families from the WebFonts facility, described in



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        CSS 2.1 [W3C.REC-CSS2-20110607], section 15, Fonts.  In
        particular, the SVG 'font' element is not allowed.

3.  How to create SVG drawings

   Many drawing packages can be used to create SVG drawings, for example
   Open Source packages Inkscape and Dia.  Be aware that such packages
   may use SVG elements or attributes that are not allowed in SVG 1.2
   RFC.  For example, the 'marker' attribute is often used to place
   symbols such as arrowheads on lines, but 'marker' is not allowed in
   SVG 1.2 Tiny or SVG 1.2 RFC.  In such cases one has to draw the
   arrowhead in another, simpler way.

   [We will need to provide a tools to check that a diagram only uses
   elements and attributes that are allowed in SVG 1.2 RFC.  These are
   listed in the Appendix below.]  [Diagrams produced with these
   packages may produce large SVG files that are hard to read or
   understand directly.  Perhaps we could provide a tool to strip out
   unnecccessary attributes?]

   Another way to create SVG drawings is to write programs to draw them.
   For example, using python and its svgwrite module is a pleasant
   environment (for those who like writing code).

4.  Meta-language for diagrams common in RFCs

4.1.  State Diagrams

4.2.  Sequence Digrgams

4.3.  Packet Layout Diarrams

5.  IANA Considerations

   This document does not create a new registry nor does it register any
   values in existing registries; no IANA action is required.

6.  Acknowledgements

   Thanks to the Design Team members for their helpful comments and
   suggestions for SVG 1.2 RFC.

7.  Revision History [RFC Editor please delete]

   version -00, 29 Jan 14:
      Initial version, using content from Nevil's
      emails to the Design Team.




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8.  Appendix: Elements and attributes allowed in SVG 1.2 RFC

9.  References

9.1.  Normative References

   [RFC6949]  Flanagan, H. and N. Brownlee, "RFC Series Format
              Requirements and Future Development", RFC 6949, May 2013.

   [W3C.REC-SVGTiny12-20081222]
              Grasso, A., Ferraiolo, J., Neumann, A., Jackson, D.,
              Berjon, R., Schepers, D., Lilley, C., McCormack, C.,
              Hardy, V., Emmons, A., Hayman, S., Dahlstroem, E.,
              Shellshear, A., Ramani, N., Northway, C., Andersson, O.,
              and A. Quint, "Scalable Vector Graphics (SVG) Tiny 1.2
              Specification", World Wide Web Consortium Recommendation
              REC-SVGTiny12-20081222, December 2008,
              <http://www.w3.org/TR/2008/REC-SVGTiny12-20081222>.

   [W3C.REC-CSS2-20110607]
              Celik, T., Hickson, I., Bos, B., and H. Lie, "Cascading
              Style Sheets Level 2 Revision 1 (CSS 2.1) Specification",
              World Wide Web Consortium Recommendation REC-
              CSS2-20110607, June 2011,
              <http://www.w3.org/TR/2011/REC-CSS2-20110607>.

9.2.  Informative References

   [W3C.REC-SVG11-20110816]
              Lilley, C., McCormack, C., Dengler, P., Grasso, A., Watt,
              J., Ferraiolo, J., Dahlstroem, E., Jun, F., Jackson, D.,
              and D. Schepers, "Scalable Vector Graphics (SVG) 1.1
              (Second Edition)", World Wide Web Consortium
              Recommendation REC-SVG11-20110816, August 2011,
              <http://www.w3.org/TR/2011/REC-SVG11-20110816>.

Authors' Addresses

   Nevil Brownlee
   The University of Auckland

   EMail: n.brownlee@auckland.ac.nz


   Internet Architecture Board

   EMail: iab@iab.org




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