[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: The <any/> element: bane of security or savior of versioni
For what it's worth, I've slowly come to believe that the general case for forwards compatibility is not necessarily that new content is completely ignored by older applications, but that there be some default rule for dealing with it. "Must ignore" is just one example of such a rule. It's also perfectly reasonable, and often useful, to suggest that such additional content is to be stored along with other data, perhaps that it is to be printed using some default formatting rules, etc. Note that in HTML as currently deployed, even elements not named explicitly in the spec, say <banana>, can be styled using CSS. One point of view is that HTML+CSS therefore contains all such elements in its language. Another is that <banana> is extension content, but with the rule that it still shows up in the DOM, still is scriptable, still can be styled via CSS, etc. So, I've come around to the view that Must Ignore is just an extreme case of a default processing rule. Note that if your very first step in receiving a V2 message in a V1 processor is to strip out everything that's new, you can't do things like digital signatures on it. So my suggestion is that for forwards compatibility, early versions of a language need a very well chosen default processing (or default interpretation) rule: whether the best rule is Must Ignore, and whether the rule can be implemented by a transform will depend on the circumstances and the requirements. Noah -------------------------------------- Noah Mendelsohn IBM Corporation One Rogers Street Cambridge, MA 02142 1-617-693-4036 --------------------------------------
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