[Om3] binary vs n-ary relations

[David Carlisle]

>   <apply>
>    <csymbol cd="logic1">and</csymbol>
>    <apply><csymbol cd="relation1">eq</csmbol>a b(xml:id="foo")</csmbol></apply>
>    <apply><csymbol cd="relation1">eq</csmbol><share href="foo"/> c</csmbol></apply>
>   </apply>
> 
> I must say that I like this a lot.

Normally Michael liking something is reason enough to object, but he may
have a point here.

The default presentation (at least the presentation currently used in the
CDs) goes via cmml -> OM -> pmml and currently if

<apply><eq/> a b c </apply>

maps to a thing with binary and and = then it will have a default
presentation of

(a = b) and (b = c)

which isn't really what you want.

I could make the OM->pmml stylesheet try to spot that adjacent terms are
identical and if so use the compressed layout
a = b = c
but that would mean in general comparing arbitrary XMl fragments for
equality which is a bit painful, and sometimes you may _want_ the
expanded layout.

On the other hand spotting that OMR usage is easy/quick and so it would
be easy to generate that from <apply><eq/> a b c </apply> and conversely
easy to give it a default presentation mathml layout of
a = b = c

David


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