Unicode Standard Annex #9, Unicode Bidirectional Algorithm (UBA), has a major update slated for release in September, 2013. This update is the most significant change in Unicode 6.3. The changes to the algorithm and text have been already been approved by the Unicode Technical Committee, subject to final editorial review.
The Unicode Technical Committee is encouraging implementations to test their code against the new test files and the two reference implementations during the month of July, 2013. It is vital that the interpretation of the text of the specification in UAX #9 be absolutely clear, and that the values in the test data be thoroughly tested by at least two implementations before release, because any changes after release—even to fix problems—can cause significant interoperability problems. The UBA is used for displaying all Arabic and Hebrew text on the web and in application programs, so there are significant ramifications for any changes to the algorithm.
The proposed update to UAX #9 involves a substantial extension of the UBA to allow for the implementation of isolate runs, introducing new Bidi_Class property values and formatting characters in support of that extension. There are also changes to Section 3.3.5, Resolving Neutral
and Isolate Formatting Types to resolve paired punctuation marks as a unit. For details, see http://www.unicode.org/reports/tr9/tr9-28.html