RFC 2278 (rfc2278) - Page 2 of 10
IANA Charset Registration Procedures
Alternative Format: Original Text Document
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].
Freed & Postel Best Current Practice