Andrew followed up: > Maybe what I'm really trying to ask is, if sometime in the future we > start to run out of space in the BMP, could U+9FB0 through U+9FFF be > reallocated to some new script, or is the allocation of these 80 codepoints to > the CJK block permanent and irrevocable ?
Please study the roadmap for the BMP: http://www.unicode.org/roadmaps/bmp/ There are many additional minority scripts slated for BMP allocation, but it is (in my opinion) unlikely that the proposals for more than a half-dozen or so of them will make it through the standardization process by the time Unicode 5.0 eventually rolls around. Other than these additional scripts, which are already catalogued and in various stages of research, most additions to the BMP at this point consist of random odd symbols, occasional punctuation, a few archaic or otherwise rare characters in existing scripts, and so on -- and those are just stuffed into gaps in the existing blocks. Han character encoders already have 1000's of code points on Plane 2 to play around with -- and Plane 3 to spill over into when they fill Plane 2. The problem with Han encoding is to constrain the costs of continuing to encode 1000's more variants of existing characters as independently encoded characters, rather than worrying about the space to encode them. The 80 code points in U+9FB0..U+9FFF *might* be used for something in the future -- most likely for some bunch of CJK characters which for some currently unforeseen reason gains some political traction to place them on the BMP. But realistically, by the time such an event could occur, it won't seriously matter to CJK implementations whether such additions are in the BMP or Plane 2 or Plane 3, since they will already be implementing Plane 2. In any case, let me assure everyone that with the discipline established by the roadmaps for future allocation, space on the BMP is well down on the list of serious concerns in the SC2/WG2 committee. And in the Unicode Technical Committee, it is hardly even on the radar, compared to many other issues of much greater concern to that committee about the maintenance and extension of the Unicode Standard. --Ken
