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Re: Parallel markup: Why do the links point from content to presentation?

From: David Carlisle <davidc@nag.co.uk>
Date: Tue, 20 Jan 2009 12:44:54 GMT
Message-Id: <200901201244.n0KCisIS012041@edinburgh.nag.co.uk>
To: ch.lange@jacobs-university.de
Cc: www-math@w3.org




> could you probably tell me a use case that justifies the direction of the
> links in parallel markup?  They point from the content markup to the
> presentation markup.  

I think its most natural to pint to the base (first child) of the
semantics rather than linking between annotations, and in

http://www.w3.org/TR/MathML2/chapter5.html#id.5.3.4


 
Actually I think it's usually more useful to put the content mathml in
the base of the semantics, and annotate it with presentation mathml if
you need to override the display.

Also, links work better in that direction, the mathml2 chapter 5 example
"simplifies" things a bit by only having two terms in the plus, so you
only get one "+" term, but in general
if you have

<apply><plus/><ci>a</ci><ci>b</ci><ci>c</ci><ci>d</ci></apply>

rendering as
a+b+c+d

using simple links you can make each of the <mo>+</mo> link to the same
<plus/> but you can't make the <plus/> link to each of the +.



chapter 5 (mml2 and mml3 draft) say:

In general, there will not be a one-to-one correspondence between nodes
in parallel branches. For example, a presentation tree may contain
elements, such as parentheses, that have no correspondents in the
content tree. It is therefore often useful to put the id  attributes on
the branch with the finest-grained node structure. Then all of the other
branches will have xref attributes to some subset of the id attributes. 

In absence of other criteria, the first branch of the semantics element
is a sensible choice to contain the id attributes. Applications that add
or remove annotations will then not have to re-assign attributes to the
semantics trees.  

David

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Received on Tuesday, 20 January 2009 12:45:33 GMT

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