Review of Bengali Khanda Ta and PRI-30 Feedback

Public Review Issue 30 (PRI-30) discussed the question of how to encode Bengali khanda ta. This document reviews some key issues and feedback that was received on PRI-30, which included new information that has bearing on arguments for or against different alternatives. In light of the feedback, a strong case for encoding khanda ta as a separate character is presented. Introduction The need for PRI-30 arose due to a problem in the description of the encoded representation of khanda ta in Unicode 4.0 and Indic FAQ #19. The problem was due to a description that did not fully specify interpretation of all possible sequences related to the khanda ta, and inappropriate association of khanda ta with half forms. When software developers at Microsoft and elsewhere implemented khanda ta like a half form, incorrect cluster behaviour resulted; for instance, the e-kaar matra in a sequence like < TA, VIRAMA, ZWJ, TA, VOWEL SIGN E > would reorder around the khanda ta, where the desired behaviour was to have the e-kaar position between the khanda ta and the following ta. To resolve this, developers devised an encoding sequence of < TA, VIRAMA, ZWJ, ZWNJ > to represent a non-clustering khanda ta. Because this was not specified in Unicode, however, this led to efforts to clarify what the intended encoded representation and behaviour for khanda ta is or should be. PRI-30 presented four alternate encoded representations (along with a complete specification for rendering and clustering behaviour for each), which covered the alternate possibilities that seemed to be worth of consideration at the time. It also presented arguments for and against each, based on current understanding of the issues. The four alternative models presented were: A. Khanda ta represented as < TA, VIRAMA > with ZWJ for explicit override B. Khanda ta represented as < TA, VIRAMA > with ZWJ, ZWJ + ZWNJ overrides C. Khanda ta represented as < TA, VIRAMA, ZWJ > D. Khanda ta encoded as a separate character Model A is the model that, it appears, was currently intended by the specification in section 9.2 of Unicode 4.0 for representing khanda ta. After considering pros and cons of each alternative, PRI-30 presented model A and the recommended solution. Of course, the public review issue