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5. Versions of the standards

ISO/IEC 10646 is updated from time to time by publication of amendments and additional parts; similarly, new versions of the Unicode standard are published over time. Each new version obsoletes and replaces the previous one, but implementations, and more significantly data, are not updated instantly.

Character Additions​

In general, the changes amount to adding new characters, which does not pose particular problems with old data.

The "Korean Mess"​

In 1996, Amendment 5 to the 1993 edition of ISO/IEC 10646 and Unicode 2.0 moved and expanded the Korean Hangul block, thereby making any previous data containing Hangul characters invalid under the new version. Unicode 2.0 has the same difference from Unicode 1.1.

Justification​

The justification for allowing such an incompatible change was that there were no major implementations and no significant amounts of data containing Hangul.

Commitment​

The incident has been dubbed the "Korean mess", and the relevant committees have pledged to never, ever again make such an incompatible change (see Unicode Consortium Policies [1]).

Impact on MIME Labels​

New versions, and in particular any incompatible changes, have consequences regarding MIME charset labels, to be discussed in MIME registration (Section 8).

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