PRI #205: Proposed addition of AL MARK and LEVEL DIRECTION MARK

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Date: Fri, 02 Sep 2011 13:04:36 -0700

The Unicode Technical Committee has posted a new issue for public
review and comment. Details are on the following web page:

Review period for the new item closes October 24, 2011.

Please see the page for links to discussion and relevant documents.
Briefly, the new issue is:

PRI #205 Proposed addition of AL MARK and LEVEL DIRECTION MARK

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.

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Received on Fri Sep 02 2011 - 15:11:09 CDT

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