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Joan Aliprand of the Research Libraries Group (RLG) sent me the
following regarding coverage of bibliographic characters:

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From: "Joan Aliprand" <BR.JMA@RLG%Forsythe.Stanford.EDU>
Subject: Additional info. re bibliographic standards & Unicode

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In article <19921101.003@erik.naggum.no> enag@ifi.uio.no (Erik Naggum) writes:
> I have studied the ISO Registry of Coded Character Sets to be Used with
> Escape Sequences (maintained by ECMA), and many bibliographic character
> sets include characters not found in Unicode.

Unicode does not claim to cover all extant bibliographic character sets,
only certain American and International standards and draft standards for
bibliographic use, namely:
   ANSI Z39.47 (Extended Latin alphabet) (also known as ANSEL)
   ANSI Z39.64 (East Asian Character Code)
   ISO 5426 (Extension of the Latin alphabet)
   ISO 5427 (Extension of the Cyrillic alphabet)
   ISO 5428 (Greek alphabet)
   ISO 6438 (African)
   ISO DIS 6861.2 (Cyrillic ... for historic Slavonic and European
     non-Slavonic languages)
   ISO DIS 6862.2 (Mathematical)
[The full bibliographical citation for each of these will be found in the
References section of volume 1 of "The Unicode Standard," Version 1.0
(1991).]

National bibliographic character sets registered with ECMA may include
other characters (in the Unicode sense) that are not present in Unicode
(nor in ISO 10646).  These should be proposed as additions.  [Appendix D in
volume 1 of "The Unicode Standard" tells how to propose additions to
Unicode.]

Certain characters in the extended Latin standards cited above were
deliberately not included in Unicode.  They fall into two categories:
glyphic variants, and split ligatures.

1. Glyphic Variants

The four "hooks below" that occur both in ANSEL and in ISO 5426 were
unified as two Unicode characters, U+0327 NON-SPACING CEDILLA and U+0328
NON-SPACING OGONEK.  There is some evidence that only two characters are
needed, and that bibliographic standards encode graphic variants as
discrete characters.

The ANSEL-Unicode correspondence is:
Latin F0 (Cedilla), Latin F7 (Left hook/tail) = U+0327 NON-SPACING CEDILLA
Latin F1 (Right hook), Latin F8 (Right cedilla) = U+0328 NON-SPACING OGONEK

The ISO 5426 equivalents of the ANSEL characters are:
Latin 5/0 (Cedilla), Latin 5/2 (Hook to left); and,
Latin 5/3 (Hook to right or ogonek), Latin 5/1 (Rude).

2.  Split Ligatures

The Unicode Technical Committee has deferred the issue of non-spacing marks
that extend over more than one character, and deliberately chose to exclude
the accent "halves" (a primitive solution).  The ligature sign is used in
the transliteration of languages written in Cyrillic script; the double
tilde occurs in Tagalog.

The ANSEL characters that have no mapping in Unicode (except for user
space) are:
  Latin EB (Ligature, first half)
  Latin EC (Ligature, second half)
  Latin FA (Double tilde, first half)
  Latin FB (Double tilde, second half)

The comparable characters in ISO 5426 are:
  Latin 5/13 (Left half of ligature sign and of double tilde)
  Latin 5/14 (Right half of ligature sign)
  Latin 5/15 (Right half of double tilde)


Disclaimer: The above is the personal opinion of Joan Aliprand, and should
not be construed as policy of The Research Libraries Group, Inc.





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