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Subject: RE: [xliff] RE: Call for dissent on BIDi solution Re: [xliff] bidi
As far as I remember my reasoning for the current setup was that the base method to specify directionality inline was to use the Unicode control codes. In addition to that I wanted XLIFF to be able to create tagging for the commonly occurring idioms in XML formats including XHTML / HTML5 without complicating the processing for XLIFF tools. In those formats spans of some form can have directionality attached, that can be encoded without control characters using <pc>/<sc>+<ec> for complete spans and as <sc> for the start of an orphaned span.
If we were to allow directional control on <ec> it would logically mean the end of an existing span that would cause a direction change. That would be hard to model in a straight forward way together with the Unicode BiDi algorithm. In that algorithm such an operation would normally reduce the stack level (ie level 9 -> level 8 for example). If we wanted to preserve that we would need to start at a higher level then what is usual when beginning the paragraph. Or we would prescribe modeling the end of a span as instead increasing the nesting and therefore increasing the stack level. That is of course technically possible but not intuitive. With control codes it is left up to the extractor / modifier to use the appropriate form.
<ph> was not given directionality as I did not find it common that placeholder elements was used to describe directionality of following content. It was either spans or plain control characters, that might have changed since then. In the cases placeholders had directionality it was with respect to the thing they represented not the following text.