RFC 2278 (rfc2278) - Page 2 of 10

IANA Charset Registration Procedures

RFC 2278                  Charset Registration              January 1998


2.2.  Character

   A member of a set of elements used for the organisation, control, or
   representation of data.

2.3.  Charset

   The term "charset" (see historical note below) is used here to refer
   to a method of converting a sequence of octets into a sequence of
   characters. This conversion may also optionally produce additional
   control information such as directionality indicators.

   Note that unconditional and unambiguous conversion in the other
   direction is not required, in that not all characters may be
   representable by a given charset and a charset may provide more than
   one sequence of octets to represent a particular sequence of
   characters.

   This definition is intended to allow charsets to be defined in a
   variety of different ways, from simple single-table mappings such as
   US-ASCII to complex table switching methods such as those that use
   ISO 2022's techniques, to be used as charsets.  However, the
   definition associated with a charset name must fully specify the
   mapping to be performed.  In particular, use of external profiling
   information to determine the exact mapping is not permitted.

   HISTORICAL NOTE: The term "character set" was originally used in MIME
   to describe such straightforward schemes as US-ASCII and ISO-8859-1
   which consist of a small set of characters and a simple one-to-one
   mapping from single octets to single characters. Multi-octet
   character encoding schemes and switching techniques make the
   situation much more complex. As such, the definition of this term was
   revised to emphasize both the conversion aspect of the process, and
   the term itself has been changed to "charset" to emphasize that it is
   not, after all, just a set of characters. A discussion of these
   issues as well as specification of standard terminology for use in
   the IETF appears in RFC 2130.

2.4.  Coded Character Set

   A Coded Character Set (CCS) is a mapping from a set of abstract
   characters to a set of integers. Examples of coded character sets are
   ISO 10646 [ISO-10646], US-ASCII [US-ASCII], and the ISO-8859 series
   [ISO-8859].







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