UTC/1999-023 Date: 6-9-99 Progressing TR#9 Bidi Algorithm ------------------------------------------------ After the UTC approved changes to TR#9 Mark edited and posted a version 4.0 of the TR on the web. In the months following UTC#79 great progress has been made in comparing two independently created implementations for compatibility and conformance. Since then the bidi committee has discovered that the algorithm as stated does not meet one of the original goals of supporting a style based implementation (see below). This is important since use of bidi in markup would involve such implementations. Several (limited) revisions of certain parts of the algorithms related to the handling of explicit bidi controls have been proposed to overcome the limitiations discovered. (Two versions of these are available as documents L2/99-171 and L2/99-171R). These are being reviewed by the bidi committee. As a result of these changes, it's currently not possible to achieve the same level of verification as had been achieved for the previous version of the algorithm, and it's not possible for UTC to ratify a final text at this meeting. Therefore, Mark, Ken, Lisa and Asmus met and agreed to propose the following plan of action for UTC. 1) TR#9 Version 4.0 will be used as the starting place for editing the book 2) UTC approves (reaffirms) these goals - the bidi algorithm will produce the same result wether implemented using explicit formatting codes in the text stream or whether used in a style based way, where explicit levels are supplied externally. - either style of implementations can be implemented with reasonable bounds of complexity, in particular, it can be demonstrated that the correct results can be achieved a) by the style based implementation without inserting explicit codes into the stream b) by the implementation using formatting codes without physically removing them - the bidi algorithm is verified by demonstrating that two independly created implementations produce the same results 3) The bidi committee is charged to define the change in language relative to the base text of step (1) that is needed to make the algorithm meet the goals set forth above and to verify that the algorithm meet these goals. 4) Mark Davis is appointed 'rapporteur' for the bidi committee and has the responsibility to coordinate the work of the bidi committee, collect the results and provide the final text to the editorial committee. 5) If a new stable formulation of the algorithm acceptable to the bidi committee can be developed and verified (as above) in time for the copy editing of the book, the editorial committee is empowered to use it for the book. Otherwise, the editorial commitee will use the existing (Version 4) of the algorithm as fallback for publication. Member companies with interest and experience in bidi implementations are invited to participate in the work of the bidi committee.