Arabic? English? Both? Neither?

i'm the david of which Michael Kaplan speaks in "Arabic? English? Both? Neither?"  The conversation is really very interesting and i don't think that it's over.  In the product for which my team is responsible, we need to detect the user selected locale preferences and set the flow of our client display wigets.  My team will also need to detect and pass along a flag of information about each caption: Is the string English Only (or text only written in LTR script), a mixture of Arabic (or any other language written in RTL script) and "English Only" text, or only a string of characters that are deamed all RTL.  We must also fix some punctuation mark fumbles that Michael Kaplan also addresses.  Unicode character planes allow for other impelementation options.