W3C home > Mailing lists > Public > www-math@w3.org > June 2007

Re: How to handle a where-list in MathML

From: David Carlisle <davidc@nag.co.uk>
Date: Wed, 6 Jun 2007 23:55:52 +0100
Message-Id: <200706062255.l56MtqKj024028@edinburgh.nag.co.uk>
To: r.muetzelfeldt@ed.ac.uk
Cc: www-math@w3.org


I agree with Robert that csymbol is probably better than ci but that
otherwise that's a good encoding.

An alternative viewpoint that I picked up in a previous life working in
formal systems that essentially viewed everything as a lambda expression
is that 
   2*a+3*a^2+b+b^2 WHERE a=5+c*2, b=17-d
is syntactic sugar for
  (lamda a b. 2*a+3*a^2+b+b^2)(5+c*2, 17-d)

that is first create the anonymous function of two variables
representing the bound variables in your expression, then apply that
function to the two  expressions which hold the definitions of the bound
variables.

This could be encoded directly in mathml as

<apply>
<lambda>
<bvar><ci>a</ci></bvar>
<bvar><ci>b</ci></bvar>
<apply>
<plus/>
<!-- mathml for 2*a+3*a^2+b+b^2 -->
</apply>
</lambda>
<apply>
<plus/>
<!-- mathml for 5+c*2-->
</apply>
<apply>
<plus/>
<!-- mathml for 17-d-->
</apply>
</apply>


This has the advantage of being coded in core mathml without needing any
csymbol defined operators, it has the possible disadvantages of being
possibly harder to read by humans, and possibly more likely to be
automatically "expanded out" by a system consuming the expression, just
as
<apply><plus/><mn>1</mn><mn>1</mn></apply>
might not be the best encoding of the concept 1+1 if you want it to
survive importing it into a CA system and not have it be seen as 2.

David




________________________________________________________________________
The Numerical Algorithms Group Ltd is a company registered in England
and Wales with company number 1249803. The registered office is:
Wilkinson House, Jordan Hill Road, Oxford OX2 8DR, United Kingdom.

This e-mail has been scanned for all viruses by Star. The service is
powered by MessageLabs. 
________________________________________________________________________
Received on Wednesday, 6 June 2007 22:56:01 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Saturday, 20 February 2010 06:13:00 GMT