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205 Proposed addition of AL MARK and LEVEL DIRECTION MARK 2011.10.31
Status: Closed
Originator: UTC
Informal Discussion: Forum 205
Formal Feedback: Moderated
Resolution: UTC will not be encoding a level direction mark at this time, but will continue to investigate solutions to these issues. A summary of the outcome of this issue is posted in the forum: http://www.unicode.org/forum/viewtopic.php?f=33&t=232.

Description of Issue:

The UTC is considering proposals for two characters to help address various difficult issues in bidirectional text layout. These two characters are similar to the already-encoded LRM and RLM.

  1. The proposed AL MARK (ALM) provides a direction mark with Bidi_Class AL in order to complete the set of direction marks with strong direction classes (L, R, AL). It requires no additional Bidi_Class value or change to the Unicode Bidirectional Algorithm (UBA).
  2. The proposed LEVEL DIRECTION MARK (LDM) behaves like a direction mark which dynamically takes on the resolved direction associated with the current embedding level. While the optimum implementation would use a new Bidi_Class value, this is prohibited by the Unicode Character Encoding Stability Policy. Several alternatives are described. Note: In earlier discussions the LDM was referred to as EMBEDDING LEVEL MARK (ELM).

Please see the background document for details, including alternative implementation options.

This is a moderated Public Review Issue. Discussion takes place on Forum 205. The moderator on this forum is responsible for summarizing discussion and providing formal feedback to the Unicode Technical Committee. The moderator will make summarized feedback available here by one week prior to the next UTC meeting. At that time this PRI will be opened for additional formal feedback via the reporting form.

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