From: "Peter Kirk" <[EMAIL PROTECTED]> > On 13/08/2003 11:09, Philippe Verdy wrote: > > >... For this reason, defective > >combining sequences (combining characters without a leading base > >character) should be forbidden (invalid for XML). > > > > > If there is even the remotest possibility of this happening, we need to > know quickly! Defective combining sequences are legal Unicode and are > now being suggested for use in Hebrew e.g. for holam male. But such a > definition would be useless if XML restricts the texts it can represent > to a subset of Unicode excluding such sequences.
I did not notice that the discussion about Hebrew holam male was related. In fact I don't know anything about the hebrew alphabet so I could not understand the semantics discussed, and so di not note that <holam, vav> was a "defective" encoding (in terms of combining sequences). When using the term "forbidden", it was only related to possible security problems with XML, but the term was certainly too much expeditive. However, given that possible security and parsing issues do exist, the case of <holam, vav> used to encode "holam-male" may be another argument to propose a neutral/invisible base character for combining characters. For the case of Hebrew, it then needs to have a "letter" behavior, but for the case of other isolated diacritics in Latin,Greek Cyrillic, and probably also Hiragana, Katakana (voice marks) it should better be handled as a symbol. I suggested several semantics for this invisible character(s) in a earlier message: - A invisible symbol - An invisible LTR letter - An invisible RTL letter all of them having a *compatibility* decomposition (or NFKD form) as a SPACE like other existing spacing combining marks, but not being canonical equivalent of SPACE (to keep separately the legacy semantics, properties, behavior and known caveats unchanged and implementation/usage-dependant, as they are now with SPACE+NSM which could then be discouraged in Unicode and strongly deprecated in SGML/HTML/XML)
