UTC/1999-020 (text) Diagram is at From: John Jenkins [jenkins@apple.com] Subject: Diagram and language The diagram (which should become figure 10-8) is also on the book ftp site in INCOMING/jhj/Diagram.pdf. Also insert the following text into the section on Ideographic Description Characters, immediately before the sub-subsection on "Equivalence": "The fact that Ideographic Description Sequences can contain other Ideographic Description Sequences means that implementations may need to be aware of the recursion depth of a sequence and its back-scan length. The recursion depth of an Ideographic Description Sequence is the maximum number of pending operations encountered in the process of parsing an Ideographic Description Sequence. In Figure 10-8 the maximum recursion depth is on the third line, where three operations are still pending when you come to the end of the IDS. "The back-scan length is the maximum number ideographs unbroken by Ideographic Description Characters in the IDS. None of the examples in Figure 10-8 have more than two ideographs in a row; for all, the back-scan depth is two. If you access the middle of a text stream and encounter an ideograph, the back-scan length tells you how far backwards you have to go to know whether or not the ideograph is part of an Ideographic Description Sequence. In the examples, you never have to go back more than two characters. "The Unicode Standard places no limits on the recursion depth of Ideographic Description Sequences. It does, however, limit the back-scan depth for valid Ideographic Description Sequences to be five or less. This is to simplify the work done by Unicode implementations that parse Ideographic Description Sequences." Looking over chapter 10: Table 10-1 is OK except that we appear to have an extraneous "KS" in the cell immediately after the "U source:" Do we still want an example of how "it may be desired to treat the Ideographic Description Sequence as a ligature of the individual characters for purposes of hit-testing, cursor movement, and other user interface operations"? We also need two in-line graphics for the "water" radical: in its full form and in its three-dot form. How should these be delivered? In §10.6 (Yi), we have an "XXX" in "Naming conventions and order" that I'm supposed to fill in. The answer is "high tone" (per ISO/IEC JTC1/SC2/WG21481). "-t" is the high tone, "-p" is the low tone, "-x" is the middle high tone, and no tone mark is the middle low tone. ===== John H. Jenkins jenkins@apple.com tseng@blueneptune.com http://www.blueneptune.com/~tseng