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Re: XML and required DTDs



At 10:45 PM 09/17/96 GMT, Charles F. Goldfarb wrote:

>>I do see need for keeping mixed content; it's just so messy to have to tag
every
>>pseudo-element as a real element. 
>It doesn't have to be that way. With a few fixed shortrefs, it can be no worse
>than some of the  proposals for enriching tag delimiters. For example, all of
>the following three equivalent alternatives can trivially be produced from
>instances of arbitrary DTDs and trivially transformed without loss between SGML
>and XML.

That pushes up implementation complexity, because there are a bunch of extra
rules. It also forces anyone typing markup to remember to put *something*,
however small, around every pseudo-element, which I find prohibitively
burdensome.

>Unfortunately, the existing proposals for handling whitespace don't  work (see
>earlier postings from myself and James Clark). There are only two solutions
that
>do:

They only "don't work" if we choose certain decision regarding the
ultra-fine details of what constitutes compatibility. As a proof-of-concept,
we could state a rule of XML that whitespace is normalized for data content
(that is, removed entirely at the beginning and end of elements and
pseudo-elements, and normalize to a single space elsewhere). One can
certainly state the same rule as an application convention applicable to
certain SGML documents that choose to use it. Yes, the ESIS is a tiny bit
different, but it has no processing consequences because we state that the
semantics of XML documents prohibit doing any different processing based on
that tiny different.

Also, ESIS is not carved in stone here; we've said from the beginning that
we may have to add or subtract from ESIS slightly to get the level of
abstractness we desire, and on which we will define equivalence. Likewise,
we can keep mixed content but constrain it in some way so the problems don't
arise (the most obvious being to prohibit things like non-|* models, etc).

S


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