[om] Re: Indexed vars

[David Carlisle]

  a) restrict content of a variable to foreign objects (e.g. MathML 
  presentation XML) -- these are non-semantic by nature, anyway.

I see no need to allow this in OM. Openmath objects (unlike MML ones)
have no default presentation anyway so there is not a lot to be gained
by saying that a variabe is red (say) if you can not colour the rest of
the object.

The fact that mathml bvar allows content greatly complicates the notion
of equality how do you recognise that a variable in scope _is_ the
bound variable. MathML 2 2nd ed has some clarifying words here
(From Michael, originally if I recall) but teh end result is that the
content does affect the semantics (you can have two separate bound
variables: red x and blue x)

http://www.w3.org/TR/MathML2/chapter4.html#contm.bvar



  b) do not allow content of a variable, but use attribution (the 
  non-semantic variety). 

I still prefer this. (either attribution, or using the bound variable as
representing a structured object and using a selector function from
some CD to gain the effect of indexed variables.


  I think that some of David's comments correspond (roughly) to b)  
  ("backing out", I think he phrased it)

yes. (reverting to the OM1 position).


  Thus, an index "i" within a 
  variable or within an attribute value of a non-semantic attribution 
  would almost certainly be interpreted to be bound by a surrounding 
  binding element with a bound variable "i".

I must be confused as to what you intend here (perhaps you need to post
an example) but I would certainly want to ensure that _all_ occurrences
of an OMV name="i" were bound (and could be alpha-converted) if
countained in an OMBIND specifiying OMV name="i".

David

-- 
http://www.dcarlisle.demon.co.uk/matthew

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