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RFC 2880 - Internet Fax T.30 Feature Mapping


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Network Working Group                                        L. McIntyre
Request for Comments: 2880                             Xerox Corporation
Category: Informational                                         G. Klyne
                                                    Content Technologies
                                                             August 2000

                   Internet Fax T.30 Feature Mapping

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 (2000).  All Rights Reserved.

Abstract

   This document describes how to map Group 3 fax capability
   identification bits, described in ITU T.30 [6], into the Internet fax
   feature schema described in "Content feature schema for Internet fax"
   [4].

   This is a companion to the fax feature schema document [4], which
   itself defines a profile of the media feature registration mechanisms
   [1,2,3], for use in performing capability identification between
   extended Internet fax systems [5].

Table of Contents

   1. Introduction .............................................3
      1.1 Organization of this document ........................3
      1.2 Terminology and document conventions .................3
      1.3 Discussion of this document ..........................4
   2. Combining feature tags ...................................4
      2.1 Relationship to Group 3 fax ..........................5
      2.2 Feature set descriptions .............................5
      2.3 Examples .............................................5
        2.3.1 Data resource example ............................6
        2.3.2 Recipient capabilities example ...................6
   3. Survey of media-related T.30 capability bits .............6
      3.1 DIS/DTC bit 15 (resolution) ..........................6
      3.2 DIS/DTC bit 16 (MR coding) ...........................7
      3.3 DIS/DTC bits 17,18 (width) ...........................7
      3.4 DIS/DTC bits 19,20 (length) ..........................7

      3.5 DIS/DTC bit 31 (MMR coding) ..........................7
      3.6 DIS/DTC bit 36 (JBIG multi-level coding) .............8
      3.7 DIS/DTC bit 37 (plane interleave) ....................8
      3.8 DIS/DTC bits 41,42,43 (resolution) ...................8
      3.9 DIS/DTC bits 44,45 (preferred units) .................9
      3.10 DIS/DTC bit 68 (JPEG) ...............................9
      3.11 DIS/DTC bit 69 (colour) .............................9
      3.12 DIS/DTC bit 71 (bits/sample) .......................10
      3.13 DIS/DTC bit 73 (no subsampling) ....................10
      3.14 DIS/DTC bit 74 (custom illuminant) .................10
      3.15 DIS/DTC bit 75 (custom gamut) ......................10
      3.16 DIS/DTC bits 76,77 (paper size) ....................11
      3.17 DIS/DTC bit 78 (JBIG bi-level coding) ..............11
      3.18 DIS/DTC bit 79 (JBIG stripe size) ..................11
      3.19 DIS/DTC bit 92,93,94 (MRC maximum functional mode) .11
      3.20 DIS/DTC bit 95 (MRC stripe size) ...................12
      3.21 DIS/DTC bit 97 (resolution) ........................12
      3.22 DIS/DTC bit 98 (resolution) ........................12
   4. Summary of T.30 capability dependencies .................12
      4.1 Image coding ........................................13
        4.1.1 Bi-level coding .................................13
        4.1.2 Multi-level coding ..............................14
        4.1.3 MRC format ......................................14
      4.2 Resolution and units ................................15
      4.3 Colour capabilities .................................17
      4.4 Document size .......................................18
   5. Mapping T.30 capabilities to fax feature schema .........18
      5.1 Image coding ........................................20
        5.1.1 Bi-level coding .................................20
        5.1.2 Multi-level coding ..............................21
        5.1.3 MRC format ......................................23
      5.2 Resolution and units ................................23
      5.3 Colour capabilities .................................24
      5.4 Document size .......................................26
   6. Examples ................................................26
      6.1 Common black-and-white fax machine ..................27
        6.1.1 Corresponding Internet fax capabilities .........29
      6.2 Full-featured color fax machine .....................30
   7. Security Considerations .................................34
   8. Acknowledgements ........................................34
   9. References ..............................................34
   10. Authors' Addresses .....................................36
   Full Copyright Statement ...................................37

1. Introduction

   This document describes how to map Group 3 fax capability
   identification bits, described in ITU T.30 [6], into the Internet fax
   feature schema described in "Content feature schema for Internet fax"
   [4].

   This is a companion to the fax feature schema document [4], which
   itself defines a profile of the media feature registration mechanisms
   [1,2,3], for use in performing capability identification between
   extended Internet fax systems [5].

1.1 Organization of this document

   Section 2 introduces the mechanisms that combine feature tag
   constraints to describe complex recipient capabilities.

   Section 3 surveys Group 3 fax (T.30) capability bits that relate to
   media handling capabilities.

   Section 4 describes the dependencies between Group 3 fax (T.30)
   capability bits.  These are presented in a decision table format [16]
   with descriptive text in place of the action bodies.

   Section 5 describes a formal mechanism for converting Group 3 fax
   (T.30) capability masks to fax feature schema statements.  The
   conversion process is driven by the decision tables introduced
   previously, using fax feature schema statements and combining rules
   in the action bodies.

   Section 6 presents an example of a Group 3 fax (T.30) capability
   mask, and uses the formal mechanism described previously to convert
   that into a corresponding fax feature schema statement.

1.2 Terminology and document conventions

   eifax system
             is used to describe any software, device or combination
             of these that conforms to the specification "Extended
             Facsimile Using Internet Mail" [5].

   Feature   is used as defined in [15].  (See also section 2 of this
             memo.)

   Feature tag
             is used as defined in [15].  (See also section 2.)

   Feature collection
             is used as defined in [2].  (See also section 2.)

   Feature set
             is used as defined in [2].  (See also section 2.)

1.3 Discussion of this document

   Discussion of this document should take place on the Internet fax
   mailing list hosted by the Internet Mail Consortium (IMC).  Please
   send comments regarding this document to:

       ietf-fax@imc.org

   To subscribe to this list, send a message with the body 'subscribe'
   to "ietf-fax-request@imc.org".

   To see what has gone on before you subscribed, please see the mailing
   list archive at:

       http://www.imc.org/ietf-fax/

2. Combining feature tags

   A fax document can be described by media features.  Any single media
   feature value can be thought of as just one component of a feature
   collection that describes some instance of a document (e.g.  a
   printed fax, a displayed image, etc.).  Such a feature collection
   consists of a number of media feature tags (each per [1]) and
   associated feature values.

   A feature set contains a number of feature collections.  Thus, a
   feature set can describe a number of different fax document
   instances.  These can correspond to different treatments of a single
   document (e.g. different resolutions used for printing a given fax),
   a number of different documents subjected to a common treatment (e.g.
   the range of different images that can be rendered on a given
   display), or some combination of these (see examples below).

   Thus, a description of a feature set can describe the rendering
   requirements of a fax document or the capabilities of a receiving
   eifax system.

2.1 Relationship to Group 3 fax

   A "feature tag" can be compared with a single bit in a T.30 DCS
   frame, describing a specific attribute of a specific fax document.

   A "feature collection" corresponds to a complete T.30 DCS frame,
   describing a range of attributes of a specific fax document.

   A "feature set" corresponds to a DIS or DTC frame, describing the
   range of document attributes that can be accepted by a given fax
   machine.

   Within T.30 DIS/DTC frames, dependencies between the various
   capabilities are implicit in the definitions of the capabilities.
   E.g. multi-level coding (DIS/DTC bit 68) requires support for
   200*200dpi resolution (DIS/DTC bit 15).  In the feature set
   description framework used by eifax systems [1,2,3,4] such
   dependencies between different features are expressed explicitly.
   Later sections of this memo describe how the implicit dependencies of
   T.30 are expressed using the media feature set notation.

2.2 Feature set descriptions

   The general approach to describing feature sets, described more fully
   in [2], is to use functions ("predicates") that, when applied to a
   feature collection value, yield a Boolean value that is TRUE if the
   feature collection describes an acceptable fax document instance,
   otherwise FALSE.

                      P(F)
        P(F) = TRUE <- : -> P(F) = FALSE
                       :
            +----------:----------+  This box represents some
            |          :          |  universe of fax documents (F)
            | Included : Excluded |  from which some acceptable subset
            |          :          |  is selected by the predicate P.
            +----------:----------+
                       :

2.3 Examples

   In the examples below the following notation is used:

      (x ? y)             tests feature tag 'x' for some relationship
                          with value 'y'.

      (| p1 p2 ... pn )   represents the logical-OR of predicates 'p1',
                          'p2' up to 'pn'.

      (& p1 p2 ... pn )   represents the logical-AND of predicates
                          'p1', 'p2' up to 'pn'.

2.3.1 Data resource example

   The following expression uses the syntax of [2] to describe a data
   resource that can be displayed either:
   (a)  as a 750x500 pixel image using 15 colours, or
   (b)  at 150dpi on an A4 page.

      (| (& (pix-x=750) (pix-y=500) (color=15) )
         (& (dpi>=150) (papersize=A4) ) )

2.3.2 Recipient capabilities example

   The following expression describes a receiving system that has:
   (a)  a screen capable of displaying 640*480 pixels and 16 million
        colours (24 bits per pixel), 800*600 pixels and 64 thousand
        colours (16 bits per pixel) or 1024*768 pixels and 256 colours
        (8 bits per pixel), or
   (b)  a printer capable of rendering 300dpi on A4 paper.

      (| (& (| (& (pix-x<=640)  (pix-y<=480) (color<=16777216) )
               (& (pix-x<=800)  (pix-y<=600) (color<=65535) )
               (& (pix-x<=1024) (pix-y<=768) (color<=256) ) )
            (media=screen) )
         (& (dpi=300)
            (media=stationery) (papersize=A4) ) )

3. Survey of media-related T.30 capability bits

   The following sections refer to T.30 DIS/DTC bits identified and
   described in Table 2/T.30 and accompanying notes [6].  Bit numbers
   that are not referenced below are considered to be not related to
   media features, hence not relevant to the Internet fax feature
   schema.

         NOTE: some of the DIS/DTC bits identified below are
         documented in revisions of the T.30 specification that
         may be not yet publicly available from the ITU.

3.1 DIS/DTC bit 15 (resolution)

   All Group 3 fax systems are required to support a basic resolution of
   200*100dpi (dots per inch) or 8*3.85dpmm (dots per millimetre).

   Setting this bit indicates additional support for 200*200dpi or
   8*7.7dpmm.

   For multi-level images, 200*200dpi is the basic resolution, and this
   bit must be set.  The other basic resolution options apply to bi-
   level images only.

   See also: bits 44,45.

3.2 DIS/DTC bit 16 (MR coding)

   All Group 3 fax systems are required to support Modified Huffman (MH)
   1-dimensional coding for bi-level images.  (A bi-level image is one
   with just two pixel states such as black and white, as opposed to a
   grey-scale or colour image.)

   Setting this bit indicates additional support for Modified Read (MR)
   2-dimensional coding for bi-level images.

   Both MH and MR coding are described in ITU T.4 [7].

   See also: bits 31,78,79.

3.3 DIS/DTC bits 17,18 (width)

   All Group 3 fax systems are required to support 215mm paper width.
   These bits can be set to indicate additional support for 255mm and
   303mm paper widths.

   See also: bits 76,77.

3.4 DIS/DTC bits 19,20 (length)

   All Group 3 fax systems are required to support 297mm paper length.
   These bits can be set to indicate additional support for 364mm and
   unlimited paper lengths.

   See also: bits 76,77.

3.5 DIS/DTC bit 31 (MMR coding)

   Setting this bit indicates support for Modified Modified Read (MMR)
   2-dimensional coding for bi-level images, in addition to the required
   support for MH coding.

   MMR coding is described in ITU T.6 [8].

   See also: bits 16,78,79.

3.6 DIS/DTC bit 36 (JBIG multi-level coding)

   If multi-level images are to be handled, support for JPEG coding is
   required (i.e. bit 68 must be set).  Setting bit 36 indicates
   additional support for JBIG lossless coding of multi-level images.

   JBIG coding for multi-level images is described in ITU T.43 [10] and
   T.4 Annex G [7].

   See also: bits 68,69.

3.7 DIS/DTC bit 37 (plane interleave)

   Setting this bit indicates support for plane interleave for JBIG-
   coded multi-level images in addition to stripe interleave, which is
   standard for JBIG multi-level images.

   JBIG coding for multi-level images is described in ITU T.43 [10] and
   T.4 Annex G [7].

   See also: bit 36.

3.8 DIS/DTC bits 41,42,43 (resolution)

   Setting these bits indicates support for resolutions in addition to
   200*100dpi and 200*200dpi, or 8*3.85dpmm and 8*7.7dpmm.  (Or in
   addition to the basic 200*200dpi resolution when using a multi-level
   image mode.)

   Bit 41 indicates support for 8*15.4dpmm bi-level images
   (independently of the settings of bits 44 and 45).

   Bit 42 indicates support for 300*300dpi bi-level images
   (independently of the settings of bits 44 and 45).  Also applies to
   multi-level images or MRC mask if bit 97 is set.

   Bit 43 indicates support for 400*400dpi and/or 16*15.4dpmm bi-level
   images, depending upon the settings of bits 44 and 45.  Also applies
   to multi-level images or MRC mask if bit 97 is set.

   See also: bits 15,44,45,97.

3.9 DIS/DTC bits 44,45 (preferred units)

   These bits are used to indicate the preferred resolution units for
   received images.  Because the exact resolution and x/y pixel density
   measures in dpi or dpmm are slightly different, some image size and
   aspect ratio distortion may occur if the sender and receiver use
   different units.

   Even when sender and recipient have different preferred units, image
   transfer must be accomplished.  For most fax uses, the dpi and dpmm
   measurements are sufficiently close to each other that the difference
   is not noticed.

   The preferred units setting affects the detailed interpretation of
   the following resolutions:

                dpi       dpmm      (dpi equivalent)
                ---       ----
      Base      200*100   8*3.85    204*98
      Bit 15    200*200   8*7.7     204*196
      Bit 43    400*400   16*15.4   408*391

   But terminals are required to accept the inch- and metric-based
   measures given above as equivalent, distorting the image if necessary
   to accommodate the differences.

   See also: bits 15, 43

3.10 DIS/DTC bit 68 (JPEG)

   This bit indicates support for JPEG coding of multi-level images.

   JPEG coding for multi-level images is described in ITU T.81 [12] and
   T.4 Annex E [7].

   See also: bits 15,69,73

3.11 DIS/DTC bit 69 (colour)

   This bit indicates support for colour images, in addition to just
   grey-scale.

   Both grey-scale and colour require multi-level coding.  The
   difference is that grey is single component while colour is multi-
   component.

   See also: bits 36,68,73.

3.12 DIS/DTC bit 71 (bits/sample)

   Standard support for multi-level images uses 8 bits per sample.
   Setting this bit indicates additional support for 12 bits per sample.

   For a grey-scale multi-level image, there is just one sample per
   pixel, giving 256 or 4096 possible pixel values.  For a full colour
   multi-level image there are three samples per pixel, giving 256^3
   (16777216) or 4096^3 (6871946736) possible values.

   When related to a mapped colour image, bit 71 also affects the
   maximum number of entries in the mapping table:  when it is reset, up
   to 4096 different pixel values can be used;  when set, up to 65536
   different values can be used.

   See also: bit 68.

3.13 DIS/DTC bit 73 (no subsampling)

   Standard support for JPEG-coded multi-level images uses 4:1:1
   chrominance subsampling.  That is, for each 4 luminance samples in
   the image data there is a single chrominance sample.

   Setting this bit indicates that JPEG-coded colour images without
   subsampling can also be supported.  This is not applicable to JBIG
   coding (bit 36).

   See also: bits 68,69.

3.14 DIS/DTC bit 74 (custom illuminant)

   Standard support for multi-level images requires use of D50
   illuminant.  Setting this bit indicates that a custom illuminant also
   can be supported for multi-level images (both grey-scale and colour).
   Details of the custom illuminant are contained in the image data.

   Use of a custom illuminant with multi-level images is described in
   ITU T.4 Annex E [7].

   See also: bits 36,68.

3.15 DIS/DTC bit 75 (custom gamut)

   Standard support for a default colour gamut is required for multi-
   level images.  Setting this bit indicates that a custom gamut also
   can be supported for multi-level images (both grey-scale and colour).
   Details of the custom gamut are contained in the image data.

   The default gamut (L*=[0,100], a*=[-85, 85], b* = [-75, 125]), and
   use of a custom gamut with multi-level images is described in ITU
   T.42 [9] and T.4 Annex E [7].

   See also: bits 36,68.

3.16 DIS/DTC bits 76,77 (paper size)

   All Group 3 faxes are required to support A4 paper size.  These bits
   can be set to indicate additional support for North American letter
   and legal paper sizes.

   See also: bits 17,18,19,20.

3.17 DIS/DTC bit 78 (JBIG bi-level coding)

   Setting bit 78 indicates support for JBIG coding of bi-level images
   (using T.85 encoding rules), in addition to the required support for
   MH coding.

   JBIG coding of bi-level images is described in ITU T.85 [14].

   See also: bits 16,31,79.

3.18 DIS/DTC bit 79 (JBIG stripe size)

   Setting bit 79 (along with bit 78) indicates support for the 'LO'
   option with JBIG coded bi-level images.  Basic bi-level JBIG coding
   uses 128 lines per stripe;  the 'LO' option allows other stripe sizes
   to be used.

   The stripe size is used for all stripes except the last, which may
   have fewer lines than the indicated value.

   JBIG coding of bi-level images is described in ITU T.85 [14].

   See also: bits 16,31,78.

3.19 DIS/DTC bit 92,93,94 (MRC maximum functional mode)

   If these bits are all zero, then Mixed Raster Content (MRC) coding is
   not supported.  Otherwise, they represent a number in the range 1-7
   that indicates an MRC maximum functional mode.

   MRC coding of images is described in ITU T.44 [11] and T.4 Annex H
   [17].

   See also: bits 68,95.

3.20 DIS/DTC bit 95 (MRC stripe size)

   Standard support for MRC uses a maximum stripe size of 256 lines.
   When this bit is set, the maximum stripe size is a full page.

   This bit is meaningful only if bits 92-94 indicate an MRC coding
   capability.  MRC coding of images is described in ITU T.44 [11] and
   T.4 Annex H [17].

   See also: bits 92,93,94.

3.21 DIS/DTC bit 97 (resolution)

   Setting this bit indicates that the additional resolutions indicated
   by bits 42 and 43 may be used for multi-level images and any MRC mask
   layer.

   When this bit is set, bit 42 implies 300dpi and bit 43 implies 400dpi
   for multi-level or MRC mask layer images (irrespective of the
   preferred units indicated by bits 44 and 45).

   See also: bits 42,43,68.

3.22 DIS/DTC bit 98 (resolution)

   Setting this bit indicates that the additional resolution 100*100dpi
   may be used for multi-level images.

        NOTE: 100dpi is not used for bi-level images, including
        the MRC mask layer.

   See also: bit 36,68,92-94.

4. Summary of T.30 capability dependencies

   This section contains a number of decision tables that indicate the
   allowable combinations of T.30 DIS/DTC mask bits.

   Within the decision table bodies, the following symbols are use to
   indicate values of T.30 DIS/DTC bits:

      0  = bit set to '0'
      1  = bit set to '1'
      x  = don't care bit value: may be '0' or '1'
      *0 = bit must be '0' ('1' is invalid in given combination)
      *1 = bit must be '1' ('0' is invalid in given combination)
      #  = bits in row combined to form a numeric value

4.1 Image coding

   MH coding is required as a minimum for Group 3 fax operation.

4.1.1 Bi-level coding

<------- T.30 bits --------->
15|16|31|36|37|68|69|73|78|79||Description
--+--+--+--+--+--+--+--+--+--++---------------------------------------
 x| 0| 0|  |  |  |  |  | 0| 0||Compression = [MH]
 x| 1| 0|  |  |  |  |  | 0| 0||Compression = [MH,MR]
 x| 0| 1|  |  |  |  |  | 0| 0||Compression = [MH,MMR]
 x| 1| 1|  |  |  |  |  | 0| 0||Compression = [MH,MR,MMR]
 x| 0| 0|  |  |  |  |  | 1| 0||Compression = [MH,T.85]
 x| 1| 0|  |  |  |  |  | 1| 0||Compression = [MH,MR,T.85]
 x| 0| 1|  |  |  |  |  | 1| 0||Compression = [MH,MMR,T.85]
 x| 1| 1|  |  |  |  |  | 1| 0||Compression = [MH,MR,MMR,T.85]
 x| 0| 0|  |  |  |  |  |*1| 1||Compression = [MH,T.85,T.85LO]
 x| 1| 0|  |  |  |  |  |*1| 1||Compression = [MH,MR,T.85,T.85LO]
 x| 0| 1|  |  |  |  |  |*1| 1||Compression = [MH,MMR,T.85,T.85LO]
 x| 1| 1|  |  |  |  |  |*1| 1||Compression = [MH,MR,MMR,T.85,T.85LO]
  |  |  |  |  |  |  |  |  |  ||MH     = 1-D per T.4
  |  |  |  |  |  |  |  |  |  ||MR     = 2-D per T.4
  |  |  |  |  |  |  |  |  |  ||MMR    = 2-D per T.6
  |  |  |  |  |  |  |  |  |  ||T.85   = Basic JBIG per T.85
  |  |  |  |  |  |  |  |  |  ||T.85LO = Optional LO with T.85/JBIG
  |  |  |  |  |  |  |  |  |  ||(Basic JBIG is 128 lines/stripe;  LO
  |  |  |  |  |  |  |  |  |  || allows other stripe sizes to be used)
--+--+--+--+--+--+--+--+--+--++---------------------------------------

4.1.2 Multi-level coding

   Note: When 37, 69, 73, 79 and 95 are set to "1", the feature
   represented by "0" is also available.  Example: If plane interleave
   is available then stripe interleave is also available.

<------- T.30 bits --------->
15|16|31|36|37|68|69|73|78|79||Description
--+--+--+--+--+--+--+--+--+--++---------------------------------------
 x|  |  |*0| x| 0| x| x|  |  ||No grey or colour (no T.43 or JPEG)
*1|  |  | 0| x| 1| 0| x|  |  ||JPEG, grey scale only
*1|  |  | 0| x| 1| 1| 0|  |  ||JPEG, full colour, subsampling
*1|  |  | 0| x| 1| 1| 1|  |  ||JPEG, full colour, no subsampling
*1|  |  | 1| 0|*1| 0| x|  |  ||T.43, JPEG, grey only, stripe i/l
*1|  |  | 1| 1|*1| 0| x|  |  ||T.43, JPEG, grey only, plane i/l
*1|  |  | 1| 0|*1| 1| 0|  |  ||T.43, JPEG, colour, stripe i/l, s/s
*1|  |  | 1| 0|*1| 1| 1|  |  ||T.43, JPEG, colour, stripe i/l, no s/s
*1|  |  | 1| 1|*1| 1| 0|  |  ||T.43, JPEG, colour, plane i/l, s/s
*1|  |  | 1| 1|*1| 1| 1|  |  ||T.43, JPEG, colour, plane i/l, no s/s
  |  |  |  |  |  |  |  |  |  ||'s/s'    is 4:1:1 L*:a*:b* subsampling
  |  |  |  |  |  |  |  |  |  ||'No s/s' is 1:1:1 L*:a*:b* subsampling
  |  |  |  |  |  |  |  |  |  ||'stripe i/l' is stripe interleave
  |  |  |  |  |  |  |  |  |  ||'plane i/l'  is full-plane interleave
--+--+--+--+--+--+--+--+--+--++---------------------------------------

4.1.3 MRC format

   Multi-level coders, as indicated above, are used for foreground and
   background images within an MRC-format document.  Bi-level codes
   are used for the mask layer.

<---- T.30 bits ------>
15|92|93|94|95|  |  |  ||Description
--+--+--+--+--+--+--+--++---------------------------------------
 x| 0| 0| 0| x|  |  |  ||MRC not accepted
*1| #| #| #| 0|  |  |  ||MRC level, max strip 256 lines
*1| #| #| #| 1|  |  |  ||MRC level, max strip full page
  |  |  |  |  |  |  |  ||### is MRC performance level (1-7, per T.44)
--+--+--+--+--+--+--+--++---------------------------------------

4.2 Resolution and units

   Support for bi-level coding at least one of 200*100dpi or 8*3.85dpmm
   is required in all cases for Group 3 fax conformance.  For multi-
   level coders (colour/grey) and MRC mask layers the base resolution is
   200*200dpi (i.e. bit 15 must be set).

   When multi-level coders (JPEG or T.43) or MRC are used, only inch-
   based square resolutions are available.  However, the base non-square
   resolution (i.e. 200x100dpi or 8x3.85dpmm) must still be available as
   a capability for use with the mandatory bi-level coder (MH).  Hence,
   any references to metric and non-square resolutions in the table
   below apply only to bi-level coders.

   When describing MRC capabilities, the complete set of usable
   resolutions is listed.  However, there are some restrictions on their
   use:  (a) 100dpi resolution can be used only with multi-level images,
   and (b) any multi-level image resolution is required to be an
   integral sub-multiple of the applicable mask resolution.

   In the following table:
      dpi  = dots per inch
      dpmm = dots per millimetre

   Preferred resolutions are indicated here, even though inch- or mm-
   based units must be accepted, according to the T.30 protocol [6].

<------- T.30 bits ------>
15|41|42|43|44|45|68|97|98||Description
--+--+--+--+--+--+--+--+--++-----------------------------------------
 0|  |  | 0| x| x|  |  |  ||Resolution = base only
  |  |  |  |  |  |  |  |  ||
 1|  |  | 0| 0| 0|  |  |  ||Invalid
 1|  |  | 0| 0| 1|  |  |  ||Resolution = 8*3.85dpmm or 8*7.7dpmm
 1|  |  | 0| 1| 0|  |  |  ||Resolution = 200*100dpi or 200*200dpi
 1|  |  | 0| 1| 1|  |  |  ||Resolution = 8*3.85dpmm or 8*7.7dpmm
  |  |  |  |  |  |  |  |  ||        or   200*100dpi or 200*200dpi
  |  |  |  |  |  |  |  |  ||
 0|  |  | 1| 0| 0|  |  |  ||Invalid
 0|  |  | 1| 0| 1|  |  |  ||Resolution = 8*3.85dpmm or 16*15.4dpmm
 0|  |  | 1| 1| 0|  |  |  ||Resolution = 200*100dpi or 400*400dpi
 0|  |  | 1| 1| 1|  |  |  ||Resolution = 8*3.85dpmm or 16*15.4dpmm
  |  |  |  |  |  |  |  |  ||        or   200*100dpi or 400*400dpi
  |  |  |  |  |  |  |  |  ||
 1|  |  | 1| 0| 0|  |  |  ||Invalid
 1|  |  | 1| 0| 1|  |  |  ||Resolution = 8*3.85dpmm or 8*7.7dpmm
  |  |  |  |  |  |  |  |  ||        or   16*15.4dpmm
 1|  |  | 1| 1| 0|  |  |  ||Resolution = 200*100dpi or 200*200dpi
  |  |  |  |  |  |  |  |  ||        or   400*400dpi
 1|  |  | 1| 1| 1|  |  |  ||Resolution = 8*7.7dpmm  or 8*7.7dpmm
  |  |  |  |  |  |  |  |  ||        or   16*15.4dpmm
  |  |  |  |  |  |  |  |  ||        or   200*100dpi or 200*200dpi
  |  |  |  |  |  |  |  |  ||        or   400*400dpi
--+--+--+--+--+--+--+--+--++-----------------------------------------
  | 0|  |  |  |  |  |  |  ||Resolutions as above
  | 1|  |  |  |  |  |  |  ||Also supports 8*15.4dpmm (bi-level only)
  |  |  |  |  |  |  |  |  ||Independent of bits 44,45
--+--+--+--+--+--+--+--+--++-----------------------------------------
  |  | 0|  |  |  |  |  |  ||Resolutions as above
  |  | 1|  |  |  |  |  |  ||Also supports 300*300dpi
  |  |  |  |  |  |  |  |  ||Independent of bits 44,45
--+--+--+--+--+--+--+--+--++-----------------------------------------
  |  |  |  |  |  | x| 0|  ||Resolutions as above
  |  |  |  |  |  |*1| 1|  ||Also 300*300dpi or 400*400dpi (see below)
  |  |  |  |  |  |  |  |  ||(Applies colour, grey-scale or MRC mask)
  |  |  |  |  |  |  |  |  ||(Valid only when bit 42 or 43 is set.)
  |  |  |  |  |  |  |  |  ||(42 => 300dpi, 43=>400dpi)
--+--+--+--+--+--+--+--+--++-----------------------------------------
  |  |  |  |  |  | x|  | 0||Resolutions as above
  |  |  |  |  |  |*1|  | 1||Also 100*100dpi
  |  |  |  |  |  |  |  |  ||(Applies colour or grey-scale only)
  |  |  |  |  |  |  |  |  ||(Independent of bits 44,45)
--+--+--+--+--+--+--+--+--++-----------------------------------------

4.3 Colour capabilities

   Bit 68 (JPEG) is required for any colour/grey scale mode, and bit 36
   indicates additional T.43 capability.

<------- T.30 bits --->
36|68|69|71|74|75|  |  ||Description
--+--+--+--+--+--+--+--++-----------------------------------------
 0| 0| x|  |  |  |  |  ||No grey scale or colour
 x| 1| 0|  |  |  |  |  ||Grey scale only
 0| 1| 1|  |  |  |  |  ||Full colour capability (CIE L*a*b*)
 1|*1| 1|  |  |  |  |  ||Full and limited colour capability:
  |  |  |  |  |  |  |  || (CIE L*a*b*, palette, RGB 1 bit/colour
  |  |  |  |  |  |  |  ||  and CMY(K)1 bit/colour)
--+--+--+--+--+--+--+--++-----------------------------------------
  | 0|  | x|  |  |  |  ||
  | 1|  | 0|  |  |  |  ||8 bits/pixel and up to 4096 palette entries
  | 1|  | 1|  |  |  |  ||8 or 12 bits/pixel, 65536 palette entries
--+--+--+--+--+--+--+--++-----------------------------------------
  | 0|  |  | x|  |  |  ||
  | 1|  |  | 0|  |  |  ||CIE standard illuminant D50 (per T.42)
  | 1|  |  | 1|  |  |  ||Custom illuminants (definition provided)
--+--+--+--+--+--+--+--++-----------------------------------------
  | 0|  |  |  | x|  |  ||
  | 1|  |  |  | 0|  |  ||Default gamut (per T.42)
  | 1|  |  |  | 1|  |  ||Custom gamuts (definition provided)
--+--+--+--+--+--+--+--++-----------------------------------------

4.4 Document size

   A4 width (215mm) is required as a minimum for Group 3 fax
   conformance.  A Group 3 fax machine must always be able to receive
   an A4 image.

<---- T.30 bits ------>
17|18|19|20|76|77|  |  ||Description
--+--+--+--+--+--+--+--++-----------------------------------------
 0| 0|  |  |  |  |  |  ||Width = 215mm
 1| 0|  |  |  |  |  |  ||Width = 215mm or 255mm
 0| 1|  |  |  |  |  |  ||Width = 215mm, 255mm or 303mm
 1| 1|  |  |  |  |  |  ||Invalid - interpret as (17=0,18=1)
  |  |  |  |  |  |  |  ||(measurements described as scan line length)
  |  |  |  |  |  |  |  ||(corresp. inch measurements: T.4 sect 2.2)
--+--+--+--+--+--+--+--++-----------------------------------------
  |  | 0| 0|  |  |  |  ||Length = 297mm (A4)
  |  | 1| 0|  |  |  |  ||Length = 297mm (A4) or 364mm (B4)
  |  | 0| 1|  |  |  |  ||Length = unlimited
  |  | 1| 1|  |  |  |  ||Invalid
--+--+--+--+--+--+--+--++-----------------------------------------
  |  |  |  | 0| 0|  |  ||Papersize = A4
  |  |  |  | 1| 0|  |  ||Papersize = A4 or NA-Letter
  |  |  |  | 0| 1|  |  ||Papersize = A4 or NA-Legal
  |  |  |  | 1| 1|  |  ||Papersize = A4 or NA-Letter or NA-Legal
  |  |  |  |  |  |  |  ||(These in addition to paper sizes implied
  |  |  |  |  |  |  |  || by bits 17-20 above)
--+--+--+--+--+--+--+--++-----------------------------------------

5. Mapping T.30 capabilities to fax feature schema

   This section follows the structure of the previous section, except
   that the decision tables are restated with feature set expression
   mappings in the action stub.  The feature set expressions use media
   feature tags presented in "Content feature schema for Internet fax"
   [4].

   To construct a feature set expression corresponding to a collection
   of DIS frame bits:

   o  Compare the DIS bits with each decision table in the following
      sections (5.1 to 5.4).  Some decision tables consist of a number
      of sub-tables separated by horizontal lines.

   o  The DIS bits will match exactly one row from each table or sub-
      table:  collect the corresponding feature set expression from the
      action stub (the right hand column of the table).

   o  In the case of the table in section 5.2, which consists of
      several sub-tables, combine the feature set expressions from each
      sub-table with a logical-OR:  (| s1 s2 ... sn ), where 's1', 's2'
      etc. are the feature set expressions selected from each sub-
      table.  In this way, a single feature set expression is obtained
      for the table.

   o  In the case of the tables in sections 5.3 and 5.4, combine the
      sub-table expressions with a logical-AND:  (& s1 s2 ... sn ).

   o  Combine the feature set expressions for each table as follows:

        (& (| T511 T512 ) T513 T52 T53 T54 )

      where:

      - T511 is the feature set expression obtained from the table in
        section 5.1.1

      - T512 is obtained from the table in section 5.1.2

      - T513 is obtained from the table in section 5.1.3

      - T52 is obtained from the table in section 5.2

      - T53 is obtained from the table in section 5.3

      - T54 is obtained from the table in section 5.4

   The resulting expression is the feature set expression corresponding
   to the DIS bits given.  Remember that there may be other capabilities
   not expressed by the DIS bits that should be incorporated into the
   final feature expression (e.g. TIFF image file structure).

   To do the reverse transformation, match the feature set to each row
   of each decision table using the matching algorithm in RFC 2533 [2],
   and OR together the DIS bit masks for each row whose feature set
   expression is completely contained by (i.e. is a subset of) that
   given (where the bit value in a table is 'x', use '0').

   A feature set A is completely contained by B if the feature set match
   of A and B (obtained by applying the feature set matching algorithm
   in [2]) is equal to A.

5.1 Image coding

5.1.1 Bi-level coding

<------- T.30 bits --------->
15|16|31|36|37|68|69|73|78|79||Feature set expression
--+--+--+--+--+--+--+--+--+--++---------------------------------------
 x| 0| 0|  |  |  |  |  | 0| 0||(& (color=binary)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[MH]) )
 x| 1| 0|  |  |  |  |  | 0| 0||(& (color=binary)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[MH,MR])
 x| 0| 1|  |  |  |  |  | 0| 0||(& (color=binary)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[MH,MMR])
 x| 1| 1|  |  |  |  |  | 0| 0||(& (color=binary)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[MH,MR,MMR])
 x| 0| 0|  |  |  |  |  | 1| 0||(& (color=binary)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[MH,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=JBIG-T85)
  |  |  |  |  |  |  |  |  |  ||   (JBIG-stripe-size=128) )
 x| 1| 0|  |  |  |  |  | 1| 0||(& (color=binary)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[MH,MR,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=JBIG-T85)
  |  |  |  |  |  |  |  |  |  ||   (JBIG-stripe-size=128) )
 x| 0| 1|  |  |  |  |  | 1| 0||(& (color=binary)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[MH,MMR,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=JBIG-T85)
  |  |  |  |  |  |  |  |  |  ||   (JBIG-stripe-size=128) )
 x| 1| 1|  |  |  |  |  | 1| 0||(& (color=binary)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[MH,MR,MMR,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=JBIG-T85)
  |  |  |  |  |  |  |  |  |  ||   (JBIG-stripe-size=128) )
 x| 0| 0|  |  |  |  |  |*1| 1||(& (color=binary)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[MH,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=JBIG-T85)
  |  |  |  |  |  |  |  |  |  ||   (JBIG-stripe-size>=0) )
 x| 1| 0|  |  |  |  |  |*1| 1||(& (color=binary)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[MH,MR,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=JBIG-T85)
  |  |  |  |  |  |  |  |  |  ||   (JBIG-stripe-size>=0) )
 x| 0| 1|  |  |  |  |  |*1| 1||(& (color=binary)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[MH,MMR,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=JBIG-T85)
  |  |  |  |  |  |  |  |  |  ||   (JBIG-stripe-size>=0) )
 x| 1| 1|  |  |  |  |  |*1| 1||(& (color=binary)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[MH,MR,MMR,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=JBIG-T85)
  |  |  |  |  |  |  |  |  |  ||   (JBIG-stripe-size>=0) )
--+--+--+--+--+--+--+--+--+--++---------------------------------------

5.1.2 Multi-level coding

<------- T.30 bits --------->
15|16|31|36|37|68|69|73|78|79||Feature set expression
--+--+--+--+--+--+--+--+--+--++---------------------------------------
 x|  |  |*0| x| 0| x| x|  |  ||
*1|  |  | 0| x| 1| 0| x|  |  ||(& (color=grey)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=JPEG)
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=JPEG-T4E) )
*1|  |  | 0| x| 1| 1| 0|  |  ||(& (color=[grey,full])
  |  |  |  |  |  |  |  |  |  ||   (image-coding=JPEG)
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=JPEG-T4E)
  |  |  |  |  |  |  |  |  |  ||   (& (color=full)
  |  |  |  |  |  |  |  |  |  ||      (color-subsampling="4:1:1") ) )
*1|  |  | 0| x| 1| 1| 1|  |  ||(& (color=[grey,full])
  |  |  |  |  |  |  |  |  |  ||   (image-coding=JPEG)
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=JPEG-T4E)
  |  |  |  |  |  |  |  |  |  ||   (& (color=full)
  |  |  |  |  |  |  |  |  |  ||      (color-subsampling=
  |  |  |  |  |  |  |  |  |  ||       ["1:1:1","4:1:1"]) ) )
*1|  |  | 1| 0|*1| 0| x|  |  ||(& (color=grey)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[JPEG,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=
  |  |  |  |  |  |  |  |  |  ||    [JPEG-T4E,JBIG-T43])
  |  |  |  |  |  |  |  |  |  ||   (image-interleave=stripe) )
*1|  |  | 1| 1|*1| 0| x|  |  ||(& (color=grey)
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[JPEG,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=
  |  |  |  |  |  |  |  |  |  ||    [JPEG-T4E,JBIG-T43])
  |  |  |  |  |  |  |  |  |  ||   (image-interleave=[stripe,plane]) )
*1|  |  | 1| 0|*1| 1| 0|  |  ||(& (color=[limited,mapped,grey,full])
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[JPEG,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=
  |  |  |  |  |  |  |  |  |  ||    [JPEG-T4E,JBIG-T43])
  |  |  |  |  |  |  |  |  |  ||   (& (color=full)
  |  |  |  |  |  |  |  |  |  ||      (color-subsampling="4:1:1"]) )
  |  |  |  |  |  |  |  |  |  ||   (image-interleave=stripe) )
*1|  |  | 1| 0|*1| 1| 1|  |  ||(& (color=[limited,mapped,grey,full])
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[JPEG,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=
  |  |  |  |  |  |  |  |  |  ||    [JPEG-T4E,JBIG-T43])
  |  |  |  |  |  |  |  |  |  ||   (& (color=full)
  |  |  |  |  |  |  |  |  |  ||      (color-subsampling=
  |  |  |  |  |  |  |  |  |  ||       ["1:1:1","4:1:1"]) )
  |  |  |  |  |  |  |  |  |  ||   (image-interleave=stripe) )

*1|  |  | 1| 1|*1| 1| 0|  |  ||(& (color=[limited,mapped,grey,full])
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[JPEG,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=
  |  |  |  |  |  |  |  |  |  ||    [JPEG-T4E,JBIG-T43])
  |  |  |  |  |  |  |  |  |  ||   (& (color=full)
  |  |  |  |  |  |  |  |  |  ||      (color-subsampling="4:1:1"]) )
  |  |  |  |  |  |  |  |  |  ||   (image-interleave=[stripe,plane]) )
*1|  |  | 1| 1|*1| 1| 1|  |  ||(& (color=[limited,mapped,grey,full])
  |  |  |  |  |  |  |  |  |  ||   (image-coding=[JPEG,JBIG])
  |  |  |  |  |  |  |  |  |  ||   (image-coding-constraint=
  |  |  |  |  |  |  |  |  |  ||    [JPEG-T4E,JBIG-T43])
  |  |  |  |  |  |  |  |  |  ||   (& (color=full)
  |  |  |  |  |  |  |  |  |  ||      (image-coding=JPEG)
  |  |  |  |  |  |  |  |  |  ||      (color-subsampling=
  |  |  |  |  |  |  |  |  |  ||       ["1:1:1","4:1:1"]) )
  |  |  |  |  |  |  |  |  |  ||   (image-interleave=[stripe,plane]) )
--+--+--+--+--+--+--+--+--+--++---------------------------------------
15|16|31|36|37|68|69|73|78|79||
--+--+--+--+--+--+--+--+--+--++---------------------------------------

5.1.3 MRC format

<---- T.30 bits ------>
15|92|93|94|95|  |  |  ||Feature set expression
--+--+--+--+--+--+--+--++---------------------------------------
 x| 0| 0| 0| x|  |  |  ||(MRC-mode=0)
*1| #| #| #| 0|  |  |  ||(& (MRC-mode<=###)
  |  |  |  |  |  |  |  ||   (MRC-max-stripe-size=[0..256]) )
*1| #| #| #| 1|  |  |  ||(& (MRC-mode<=###)
  |  |  |  |  |  |  |  ||   (MRC-max-stripe-size>=0) )
--+--+--+--+--+--+--+--++---------------------------------------

5.2 Resolution and units

<------- T.30 bits ------>
15|41|42|43|44|45|68|97|98||Feature set expression
--+--+--+--+--+--+--+--+--++-----------------------------------------
 0|  |  | 0|  |  |  |  |  ||(& (color=binary)
  |  |  |  |  |  |  |  |  ||   (| (& (dpi=200) (dpi-xyratio=200/100) )
  |  |  |  |  |  |  |  |  ||      (& (dpi=204)
  |  |  |  |  |  |  |  |  ||         (dpi-xyratio=204/98) ) ) )
  |  |  |  |  |  |  |  |  ||
 1|  |  | 0|  |  |  |  |  ||(| (& (color=binary)
  |  |  |  |  |  |  |  |  ||      (| (& (dpi=204)
  |  |  |  |  |  |  |  |  ||            (dpi-xyratio=204/98) )
  |  |  |  |  |  |  |  |  ||         (& (dpi=204)
  |  |  |  |  |  |  |  |  ||            (dpi-xyratio=204/196) )
  |  |  |  |  |  |  |  |  ||         (& (dpi=200)
  |  |  |  |  |  |  |  |  ||            (dpi-xyratio=200/100) ) ) )
  |  |  |  |  |  |  |  |  ||   (& (dpi=200) (dpi-xyratio=1) ) )
 0|  |  | 1|  |  |  |  |  ||(| (& (color=binary)
  |  |  |  |  |  |  |  |  ||      (| (& (dpi=204)
  |  |  |  |  |  |  |  |  ||            (dpi-xyratio=204/98) )
  |  |  |  |  |  |  |  |  ||         (& (dpi=408)
  |  |  |  |  |  |  |  |  ||            (dpi-xyratio=408/391) )
  |  |  |  |  |  |  |  |  ||         (& (dpi=200)
  |  |  |  |  |  |  |  |  ||            (dpi-xyratio=200/100) ) ) )
  |  |  |  |  |  |  |  |  ||   (& (dpi=400) (dpi-xyratio=1) ) )
 1|  |  | 1|  |  |  |  |  ||(| (& (color=binary)
  |  |  |  |  |  |  |  |  ||      (| (& (dpi=204)
  |  |  |  |  |  |  |  |  ||            (dpi-xyratio=204/98) )
  |  |  |  |  |  |  |  |  ||         (& (dpi=204)
  |  |  |  |  |  |  |  |  ||            (dpi-xyratio=204/196) )
  |  |  |  |  |  |  |  |  ||         (& (dpi=408)
  |  |  |  |  |  |  |  |  ||            (dpi-xyratio=408/391) )
  |  |  |  |  |  |  |  |  ||         (& (dpi=200)
  |  |  |  |  |  |  |  |  ||            (dpi-xyratio=200/100) ) ) )
  |  |  |  |  |  |  |  |  ||   (& (dpi=200) (dpi-xyratio=1) )
  |  |  |  |  |  |  |  |  ||   (& (dpi=400) (dpi-xyratio=1) ) )
--+--+--+--+--+--+--+--+--++-----------------------------------------
  | 0|  |  |  |  |  |  |  ||
  | 1|  |  |  |  |  |  |  ||(& (color=binary)
  |  |  |  |  |  |  |  |  ||   (dpi=204)
  |  |  |  |  |  |  |  |  ||   (dpi-xyratio=204/391) )
--+--+--+--+--+--+--+--+--++-----------------------------------------
  |  | 0|  |  |  |  |  |  ||
  |  | 1|  |  |  |  |  |  ||(& (dpi=300) (dpi-xyratio=1) )

--+--+--+--+--+--+--+--+--++-----------------------------------------
  |  | x| x|  |  | x| 0|  ||
  |  | x| 1|  |  |*1| 1|  ||(& (dpi=400) (dpi-xyratio=1) )
  |  |*1| 0|  |  |*1| 1|  ||
--+--+--+--+--+--+--+--+--++-----------------------------------------
  |  |  |  |  |  | x|  | 0||
  |  |  |  |  |  |*1|  | 1||(| (color=binary)
  |  |  |  |  |  |  |  |  ||   (& (color=[limited,mapped,grey,full])
  |  |  |  |  |  |  |  |  ||      (dpi=100) (dpi-xyratio=1) ) )
--+--+--+--+--+--+--+--+--++-----------------------------------------
15|41|42|43|44|45|68|97|98||
--+--+--+--+--+--+--+--+--++-----------------------------------------

   Note:  all numbers in media feature expressions are integer or
   rational values;  hence the rational number format (n/m) used here.

   Also note:  the preferred unit bits (44,45) are not tested here, as a
   Group 3 fax machine must accept and process either form of units for
   binary images.  All resolutions are expressed in dpi;  here are the
   metric unit equivalents:

   204  ~= (1728/215)*25.4  ~=  8.04dpmm expressed in dpi
   408  ~= (3456/215)*25.4  ~= 16.08dpmm expressed in dpi
    98  ~=  3.85*25.4       ~=  3.85dpmm expressed in dpi
   196  ~=  7.70*25.4       ~=  7.70dpmm expressed in dpi
   391  ~= 15.40*25.4       ~= 15.40dpmm expressed in dpi

5.3 Colour capabilities

<------- T.30 bits --->
36|68|69|71|74|75|  |  ||Feature set expression
--+--+--+--+--+--+--+--++-----------------------------------------
 0| 0| x|  |  |  |  |  ||
 x| 1| 0|  |  |  |  |  ||(| (color=binary)
  |  |  |  |  |  |  |  ||   (& (color=grey)
  |  |  |  |  |  |  |  ||      (color-space=CIELAB) ) )
 0| 1| 1|  |  |  |  |  ||(| (color=binary)
  |  |  |  |  |  |  |  ||   (& (color=[grey,full])
  |  |  |  |  |  |  |  ||      (color-space=CIELAB) ) )
 1|*1| 1|  |  |  |  |  ||(| (color=binary)
  |  |  |  |  |  |  |  ||   (& (color=limited)
  |  |  |  |  |  |  |  ||      (color-space=[Device-RGB,Device-CMY])
  |  |  |  |  |  |  |  ||      (color-levels<=8) )
  |  |  |  |  |  |  |  ||   (& (color=limited)
  |  |  |  |  |  |  |  ||      (color-space=Device-CMYK)
  |  |  |  |  |  |  |  ||      (color-levels<=16) )
  |  |  |  |  |  |  |  ||   (& (color=[mapped,grey,full])
  |  |  |  |  |  |  |  ||      (color-space=CIELAB) ) )

--+--+--+--+--+--+--+--++-----------------------------------------
  | 0|  | x|  |  |  |  ||
  | 1|  | 0|  |  |  |  ||(| (color=[binary,limited])
  |  |  |  |  |  |  |  ||   (& (color=mapped)
  |  |  |  |  |  |  |  ||      (color-levels<=4096) )
  |  |  |  |  |  |  |  ||   (& (color=grey)
  |  |  |  |  |  |  |  ||      (color-levels<=256) )
  |  |  |  |  |  |  |  ||   (& (color=full)
  |  |  |  |  |  |  |  ||      (color-levels<=16777216) ) )
  | 1|  | 1|  |  |  |  ||(| (color=[binary,limited])
  |  |  |  |  |  |  |  ||   (& (color=mapped)
  |  |  |  |  |  |  |  ||      (color-levels<=65536) )
  |  |  |  |  |  |  |  ||   (& (color=grey)
  |  |  |  |  |  |  |  ||      (color-levels<=4096) )
  |  |  |  |  |  |  |  ||   (& (color=full)
  |  |  |  |  |  |  |  ||      (color-levels<=68719476736) ) )
--+--+--+--+--+--+--+--++-----------------------------------------
  | 0|  |  | x|  |  |  ||
  | 1|  |  | 0|  |  |  ||(| (color=[binary,limited])
  |  |  |  |  |  |  |  ||   (& (color=[mapped,grey,full])
  |  |  |  |  |  |  |  ||      (color-illuminant=D50) ) )
  | 1|  |  | 1|  |  |  ||   -- Any color illuminant: D50 or custom
  |  |  |  |  |  |  |  ||   -- See note below
--+--+--+--+--+--+--+--++-----------------------------------------
  | 0|  |  |  | x|  |  ||
  | 1|  |  |  | 0|  |  ||(| (color=[binary,limited])
  |  |  |  |  |  |  |  ||   (& (color=grey)
  |  |  |  |  |  |  |  ||      (CIELAB-L-min>=0)
  |  |  |  |  |  |  |  ||      (CIELAB-L-max<=100) )
  |  |  |  |  |  |  |  ||   (& (color=[mapped,full])
  |  |  |  |  |  |  |  ||      (CIELAB-L-min>=0)
  |  |  |  |  |  |  |  ||      (CIELAB-L-max<=100)
  |  |  |  |  |  |  |  ||      (CIELAB-a-min>=-85)
  |  |  |  |  |  |  |  ||      (CIELAB-a-max<=85)
  |  |  |  |  |  |  |  ||      (CIELAB-b-min>=-75)
  |  |  |  |  |  |  |  ||      (CIELAB-b-max<=125) ) )
  | 1|  |  |  | 1|  |  ||   -- Any color gamut: default or custom
--+--+--+--+--+--+--+--++-----------------------------------------
36|68|69|71|74|75|  |  ||Feature set expression
--+--+--+--+--+--+--+--++-----------------------------------------

      NOTE: the above table assumes the registration of a feature tag
      for color illuminant, values of which are tokens that are the same
      as those described by ITU T.4 [7], Annex E, section E.6.7.

5.4 Document size

   A4 width (215mm) is required as a minimum for Group 3 fax
   conformance.  A Group 3 fax machine must always be able to receive an
   A4 image.

<---- T.30 bits ------>
17|18|19|20|76|77|  |  ||Feature set expression
--+--+--+--+--+--+--+--++-----------------------------------------
 0| 0|  |  |  |  |  |  ||(Size-x <= 2150/254)
 1| 0|  |  |  |  |  |  ||(Size-x <= 2550/254)
 x| 1|  |  |  |  |  |  ||(Size-x <= 3030/254)
--+--+--+--+--+--+--+--++-----------------------------------------
  |  | 0| 0|  |  |  |  ||(Size-y <= 2970/254)
  |  | 1| 0|  |  |  |  ||(Size-y <= 3640/254)
  |  | 0| 1|  |  |  |  ||  -- unlimited
  |  | 1| 1|  |  |  |  ||  -- invalid
--+--+--+--+--+--+--+--++-----------------------------------------
  |  |  |  | 0| 0|  |  ||(Paper-size=A4)
  |  |  |  | 1| 0|  |  ||(Paper-size=[A4,Letter])
  |  |  |  | 0| 1|  |  ||(Paper-size=[A4,Legal])
  |  |  |  | 1| 1|  |  ||(Paper-size=[A4,Letter,Legal])
--+--+--+--+--+--+--+--++-----------------------------------------

6. Examples

   NOTE:  Although motivated by the requirements of eifax [5], this
   document is concerned with describing capabilities of Group 3 fax
   systems [6].  As such, the algorithms do not of themselves create
   equivalent Internet fax capability statements but, rather, they
   construct capability expressions that might be incorporated into
   those for eifax systems.

   This point is illustrated at the end of the first example below where
   subsection 6.1.1 has been added, which combines T.30 capabilities
   with an appropriate TIFF file format capability to yield an
   expression that might be used to describe an Internet fax system.

6.1 Common black-and-white fax machine

   DIS/DTC
   Bit No.   DIS/DTC bit description                 Value
   -------   -----------------------                 -----
   15        R8 x 7.7 lines/mm and/or                1
             200 x 200 pels/25.4 mm
   16        Two dimensional coding capability       1
   17,18     Recording width capabilities:           0,0
             Scan line length 215 mm + 1%
   19,20     Recording length capability:            01
             unlimited
   31        T.6 (MMR) coding capability             1
   36        T.43 (JBIG) coding capability           0
   37        Plane interleave                        0
   41        Resolution: 8x15.4 dpmm                 0
   42        Resolution: 300x300 dpi                 1
   43        Resolution: 16x15.4 dpmm and/or 400x400 0
             dpi
   68        JPEG coding: not supported              0
   69        Full color mode: not supported          0
   71        12 bits/pel component:  not supported   0
   73        No subsampling (1:1:1):  not supported  0
   74        Custom illuminant:  not supported       0
   75        Custom gamut range:  not supported      0
   76        North American Letter paper size        1
             (8.5"x11") capability
   77        North American Legal paper size         0
             (8.5"x14") capability:  not supported
   78        Single-progression sequential coding    0
             (T.85, bi-level JBIG) basic capability:
             not supported
   79        Single-progression sequential coding    0
             (T.85, bi-level JBIG) optional L0
             capability for other than 128
             lines/stripe:  not supported
   92,93,94  T.44 (Mixed Raster Content) mode:       0,0,0
             not supported
   95        Page length maximum stripe size for MRC 0
             coding:  not supported.
   97        Multi-level resolution 300x300dpi or    0
             400x400dpi:  not supported
   98        Multi-level resolution 100x100dpi:      0
             not supported

   Following the procedure in section 5, matching these DIS bits
   against the decision tables in sections 5.1 to 5.4, we get:

      5.1.1  [Bits 16,31,78,79 = 1,1,0,0]
               (& (color=binary) (image-coding=[MH,MR,MMR]) )

      5.1.2  [Bits 15,36,37,68,69,73 = 1,0,0,0,0,0]
               -- no capabilities

      5.1.3  [Bits 15,92,93,94,95 = 1,0,0,0,0]
               (MRC-mode=0)

      5.2    [Bits 15,43 = 1,0]
               (| (& (color=binary)
                     (| (& (dpi=204)
                           (dpi-xyratio=204/98) )
                        (& (dpi=204)
                           (dpi-xyratio=204/196) )
                        (& (dpi=200)
                           (dpi-xyratio=200/100) ) ) )
                  (& (dpi=200) (dpi-xyratio=1) ) )
             [Bit 41 = 0]
               -- no capabilities
             [Bit 42 = 1]
               (& (dpi=300) (dpi-xyratio=1) )
             [Bits 42,43,68,97 = 0,0,0,0]
               -- no capabilities
             [Bits 68,98 = 0,0]
               -- no capabilities

      5.3    [Bits 36,68,69 = 0,0,0]
               -- no capabilities
             [Bits 68,71 = 0,0]
               -- no capabilities
             [Bits 68,74 = 0,0]
               -- no capabilities
             [Bits 68,75 = 0,0]
               -- no capabilities

      5.4    [Bits 17,18 = 0,0]
               (size-x<=2150/254)
             [Bits 19,20 = 0,1]
               -- no capability constraint
             [Bits 76,77 = 1,0]
               (Paper-size=[A4,Letter])

   Combining these as indicated in section 5, we get the following.
   (The initial expression is constructed verbatim per the rules in the
   first part of section 5, even though it contains some redundancy.)

      (& (| (& (color=binary) (image-coding=[MH,MR,MMR]) ) )
         (MRC-mode=0)
         (| (| (& (color=binary)
                  (| (& (dpi=204) (dpi-xyratio=204/98)  )
                     (& (dpi=204) (dpi-xyratio=204/196) )
                     (& (dpi=200) (dpi-xyratio=200/100) ) ) )
               (& (dpi=200) (dpi-xyratio=1) ) )
            (& (dpi=300) (dpi-xyratio=1) ) )
         (& (size-x<=2150/254)
            (Paper-size=[A4,Letter]) ) )

   This in turn is simplified as follows.  Note that the expression '(&
   (| (& A B ) ) C ... )' simplifies to just '(& A B C ... )'.

      (& (color=binary)
         (image-coding=[MH,MR,MMR])
         (MRC-mode=0)
         (| (& (dpi=204) (dpi-xyratio=204/98)  )
            (& (dpi=204) (dpi-xyratio=204/196) )
            (& (dpi=200) (dpi-xyratio=200/100) )
            (& (dpi=200) (dpi-xyratio=1) )
            (& (dpi=300) (dpi-xyratio=1) ) )
         (size-x<=2150/254)
         (Paper-size=[A4,Letter]) )

6.1.1 Corresponding Internet fax capabilities

   In the case of an Internet fax device, additional capabilities not
   described by the T.30 DIS frame should be included;  e.g. the
   supported TIFF file structure:

      (& (color=binary)
         (image-file-structure=[TIFF-Limited,TIFF-Minimal])
         (image-coding=[MH,MR,MMR])
         (MRC-mode=0)
         (| (& (dpi=204) (dpi-xyratio=204/98)  )
            (& (dpi=204) (dpi-xyratio=205/196) )
            (& (dpi=200) (dpi-xyratio=200/100) )
            (& (dpi=200) (dpi-xyratio=1) )
            (& (dpi=300) (dpi-xyratio=1) ) )
         (size-x<=2150/254)
         (Paper-size=[A4,Letter]) )

6.2 Full-featured color fax machine

   DIS/DTC
   Bit No.   DIS/DTC bit description                 Value
   -------   -----------------------                 -----
   15        R8 x 7.7 lines/mm and/or                1
             200 x 200 pels/25.4 mm
   16        Two dimensional coding capability       1
   17,18     Recording width capabilities:           0,0
             Scan line length 215 mm + 1%
   19,20     Recording length capability:            01
             unlimited
   31        T.6 (MMR) coding capability             1
   36        T.43 (JBIG) coding capability           0
   37        Plane interleave                        0
   41        Resolution: 8x15.4 dpmm                 1
   42        Resolution: 300x300 dpi                 0
   43        Resolution: 16x15.4 dpmm and/or 400x400 1
             dpi
   68        JPEG coding: supported                  1
   69        Full color mode: supported              1
   71        12 bits/pel component:  not supported   0
   73        No subsampling (1:1:1):  supported      1
   74        Custom illuminant:  not supported       0
   75        Custom gamut range:  not supported      0
   76        North American Letter paper size        1
             (8.5"x11") capability
   77        North American Legal paper size         0
             (8.5"x14") capability:  not supported
   78        Single-progression sequential coding    0
             (T.85, bi-level JBIG) basic capability:
             not supported
   79        Single-progression sequential coding    0
             (T.85, bi-level JBIG) optional L0
             capability for other than 128
             lines/stripe:  not supported
   92,93,94  T.44 (Mixed Raster Content) mode:       0,0,1
             mode 1 supported
   95        Page length maximum stripe size for MRC 1
             coding.
   97        Multi-level resolution 300x300dpi or    1
             400x400dpi:  supported
   98        Multi-level resolution 100x100dpi:      1
             supported

   Matching these DIS bits against the decision tables in sections 5.1
   to 5.4, we get:

      5.1.1  [Bits 16,31,78,79 = 1,1,0,0]
               (& (color=binary) (image-coding=[MH,MR,MMR]) )

      5.1.2  [Bits 15,36,37,68,69,73 = 1,0,0,1,1,1]
               (& (color=[grey,full])
                  (image-coding=JPEG)
                  (image-coding-constraint=JPEG-T4E)
                  (& (color=full)
                     (image-coding=JPEG)
                     (color-subsampling=["1:1:1","4:1:1"]) ) )

      5.1.3  [Bits 15,92,93,94,95 = 1,0,0,1,1]
               (& (MRC-mode<=1) (MRC-max-stripe-size>=0) )

      5.2    [Bits 15,43 = 1,1]
               (| (& (color=binary)
                     (| (& (dpi=204)
                           (dpi-xyratio=204/98) )
                        (& (dpi=204)
                           (dpi-xyratio=204/196) )
                        (& (dpi=408)
                           (dpi-xyratio=408/391) )
                        (& (dpi=200)
                           (dpi-xyratio=200/100) ) ) )
                  (& (dpi=200) (dpi-xyratio=1) )
                  (& (dpi=400) (dpi-xyratio=1) ) )
             [Bit 41 = 1]
               (& (color=binary)
                  (dpi=204) (dpi-xyratio=204/391) )
             [Bit 42 = 0]
               -- no capabilities
             [Bits 42,43,68,97 = 0,1,1,1]
               (& (dpi=400) (dpi-xyratio=1) )
             [Bits 68,98 = 1,1]
               (| (color=binary)
                  (& (color=[limited,mapped,grey,full])
                     (dpi=100) (dpi-xyratio=1) ) )

      5.3    [Bits 36,68,69 = 0,1,1]
               (| (color=binary)
                  (& (color=[grey,full])
                     (color-space=CIELAB) ) )
             [Bits 68,71 = 1,0]
               (| (color=[binary,limited])
                  (& (color=mapped)

                     (color-levels<=4096) )
                  (& (color=grey)
                     (color-levels<=256) )
                  (& (color=full)
                     (color-levels<=16777216) ) )
             [Bits 68,74 = 1,0]
               (| (color=[binary,limited])
                  (& (color=[mapped,grey,full])
                     (color-illuminant=D50) ) )
             [Bits 68,75 = 1,0]
               (| (color=[binary,limited])
                  (& (color=grey)
                     (CIELAB-L-min>=0)
                     (CIELAB-L-max<=100) )
                  (& (color=[mapped,full])
                     (CIELAB-L-min>=0)
                     (CIELAB-L-max<=100)
                     (CIELAB-a-min>=-85)
                     (CIELAB-a-max<=85)
                     (CIELAB-b-min>=-75)
                     (CIELAB-b-max<=125) ) )

      5.4    [Bits 17,18 = 0,0]
               (size-x<=2150/254)
             [Bits 19,20 = 0,1]
               -- no capability constraint
             [Bits 76,77 = 1,0]
               (Paper-size=[A4,Letter])

   Combining these as indicated in section 5, we get the following:

      (& (| (& (color=binary)
               (image-coding=[MH,MR,MMR]) )
            (& (color=[grey,full])
               (image-coding=JPEG)
               (image-coding-constraint=JPEG-T4E)
               (& (color=full)
                  (image-coding=JPEG)
                  (color-subsampling=["1:1:1","4:1:1"]) ) )
         (& (MRC-mode<=1) (MRC-max-stripe-size>=0) )
         (| (| (& (color=binary)
                  (| (& (dpi=204) (dpi-xyratio=204/98) )
                     (& (dpi=204) (dpi-xyratio=204/196) )
                     (& (dpi=408) (dpi-xyratio=408/391) )
                     (& (dpi=200) (dpi-xyratio=200/100) ) ) )
               (& (dpi=200) (dpi-xyratio=1) )
               (& (dpi=400) (dpi-xyratio=1) ) )
            (& (color=binary)

               (dpi=204) (dpi-xyratio=204/391) )
            (& (dpi=400) (dpi-xyratio=1) )
            (| (color=binary)
               (& (color=[limited,mapped,grey,full])
                  (dpi=100) (dpi-xyratio=1) ) ) )
         (& (| (color=binary)
               (& (color=[grey,full]) (color-space=CIELAB) ) )
            (| (color=[binary,limited])
               (& (color=mapped) (color-levels<=4096) )
               (& (color=grey) (color-levels<=256) )
               (& (color=full) (color-levels<=16777216) ) )
            (| (color=[binary,limited])
               (& (color=[mapped,grey,full]) (color-illuminant=D50) ) )
            (| (color=[binary,limited])
               (& (color=grey)
                  (CIELAB-L-min>=0)
                  (CIELAB-L-max<=100) )
               (& (color=[mapped,full])
                  (CIELAB-L-min>=0)
                  (CIELAB-L-max<=100)
                  (CIELAB-a-min>=-85)
                  (CIELAB-a-max<=85)
                  (CIELAB-b-min>=-75)
                  (CIELAB-b-max<=125) ) ) )
         (& (size-x<=2150/254)
            (Paper-size=[A4,Letter]) ) )

   This in turn simplifies to:

      (| (& (color=binary)
            (image-coding=[MH,MR,MMR])
            (MRC-mode<=1) (MRC-max-stripe-size>=0)
            (| (& (dpi=204) (dpi-xyratio=204/98) )
               (& (dpi=204) (dpi-xyratio=204/196) )
               (& (dpi=204) (dpi-xyratio=204/391) )
               (& (dpi=408) (dpi-xyratio=408/391) )
               (& (dpi=200) (dpi-xyratio=200/100) )
               (& (dpi=200) (dpi-xyratio=1) )
               (& (dpi=400) (dpi-xyratio=1) ) )
            (size-x<=2150/254)
            (Paper-size=[A4,Letter]) )
         (& (color=grey)
            (image-coding=JPEG)
            (image-coding-constraint=JPEG-T4E)
            (MRC-mode<=1) (MRC-max-stripe-size>=0)
            (dpi=[100,200,400]) (dpi-xyratio=1)
            (color-space=CIELAB)
            (color-levels<=256)

            (color-illuminant=D50)
            (CIELAB-L-min>=0)
            (CIELAB-L-max<=100)
            (size-x<=2150/254)
            (Paper-size=[A4,Letter]) )
         (& (color=full)
            (image-coding=JPEG)
            (image-coding-constraint=JPEG-T4E)
            (color-subsampling=["1:1:1","4:1:1"])
            (MRC-mode<=1) (MRC-max-stripe-size>=0)
            (dpi=[100,200,400]) (dpi-xyratio=1)
            (color-space=CIELAB)
            (color-levels<=16777216)
            (color-illuminant=D50)
            (CIELAB-L-min>=0)
            (CIELAB-L-max<=100)
            (CIELAB-a-min>=-85)
            (CIELAB-a-max<=85)
            (CIELAB-b-min>=-75)
            (CIELAB-b-max<=125)
            (size-x<=2150/254)
            (Paper-size=[A4,Letter]) ) )

7. Security Considerations

   Security considerations are discussed in the fax feature schema
   description [4].  This memo is not believed to introduce any
   additional security concerns.

8. Acknowledgements

   The authors gratefully acknowledge the following persons who made
   comments on earlier versions of this memo:  Mr. Hiroshi Tamura and
   and Dr. Robert Buckley.

9. References

   [1]  Holtman, K., Mutz, A. and T. Hardie, "Media Feature Tag
        Registration Procedure", RFC 2506, March 1999.

   [2]  Graham, K., "A syntax for describing media feature sets" RFC
        2533, March 1999.

   [3]  Masinter, L., Holtman, K., Mutz, A. and D. Wing, "Media Features
        for Display, Print, and Fax", RFC 2534, March 1999.

   [4]  Klyne, G. and L. McIntyre, "Content Feature Schema for Internet
        Fax (V2)", RFC 2879, July 2000.

   [5]  Masinter, L. and D. Wing, "Extended Facsimile Using Internet
        Mail", RFC 2532, March 1999.

   [6]  "Procedures for document facsimile transmission in the general
        switched telephone network" ITU-T Recommendation T.30 (1996),
        including Amendment 1 (1997), Amendment 2 (1997), Amendment 3
        (1998) and Amendment 4 (1999) International Telecommunications
        Union

   [7]  "Standardization of Group 3 facsimile terminals for document
        transmission" ITU-T Recommendation T.4 (1996), including
        Amendment 1 (1997), Amendment 2 (1997) and Amendment 3 (1999)
        International Telecommunications Union (Covers basic fax coding
        formats:  MH, MR; Annex E deals with some color image related
        matters, including codes for optional custom illuminants.  Annex
        G deals with some aspects of JBIG encoding of multi-level
        images.)

   [8]  "Facsimile coding schemes and coding control functions for Group
        4 facsimile apparatus" ITU Recommendation T.6 International
        Telecommunications Union (Commonly referred to as the MMR
        standard; covers extended 2-D fax coding format)

   [9]  "Continuous-tone colour representation method for facsimile"
        ITU-T Recommendation T.42 (1996) International
        Telecommunications Union (Covers custom illuminant, gamut)

   [10] "Colour and gray-scale image representation using lossless
        coding scheme for facsimile" ITU-T Recommendation T.43 (1997)
        International Telecommunications Union (Covers JBIG for
        colour/grey images)

   [11] "Mixed Raster Content (MRC)" ITU-T Recommendation T.44 (1999)
        International Telecommunications Union

   [12] "Information technology - Digital compression and coding of
        continuous-tone still image - Requirements and guidelines" ITU-T
        Recommendation T.81 (1992) | ISO/IEC 10918-1:1993 International
        Telecommunications Union (Commonly referred to as JPEG standard)

   [13] "Information technology - Coded representation of picture and
        audio information - Progressive bi-level image compression"
        ITU-T Recommendation T.82 (1993) | ISO/IEC 11544:1993
        International Telecommunications Union (Commonly referred to as
        JBIG1 standard)

   [14] "Application profile for Recommendation T.82 - Progressive bi-
        level image compression (JBIG1 coding scheme for facsimile
        apparatus)" ITU-T Recommendation T.85 (1995), including
        Amendment 1 (1996), Amendment 2 (1997) and Corrigendum 1 (1997)
        International Telecommunications Union (Covers bi-level JBIG)

   [15] Klyne, G., "Protocol-independent Content Negotiation Framework",
        RFC 2703, September 1999.

   [16] "Programs from Decision Tables" E. Humbey Macdonald/American
        Elsevier computer monographs (19), 1973 ISBN 0-444-19569-6/0-
        356-04126-3 (This is an old title, and may not be still in
        print.  It contains a number of references to decision table
        articles published in Communications of the ACM:  August 1967,
        September 1970, January 1966, November 1966, October 1968,
        January 1965, February 1964, June 1970, November 1965, June
        1965, February 1971.)

   [17] "Mixed Raster Content (MRC) mode for G3 facsimile" ITU-T
        Recommendation T.4, Annex H (1999) International
        Telecommunications Union (Covers stripe size)

10. Authors' Addresses

   Lloyd McIntyre
   Xerox Corporation
   Mailstop PAHV-121
   3400 Hillview Ave.
   Palo Alto, CA 94304 USA

   Phone: +1-650-813-6762
   Fax:   +1-650-845-2340
   EMail: Lloyd.McIntyre@pahv.xerox.com

   Graham Klyne
   Content Technologies Ltd.
   1220 Parkview,
   Arlington Business Park
   Theale
   Reading, RG7 4SA
   United Kingdom

   Phone: +44 118 930 1300
   Fax:   +44 118 930 1301
   EMail: GK@ACM.ORG

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