[om] comments on documents

David Carlisle davidc at nag.co.uk
Fri May 17 19:05:48 CEST 2002

> Well, the MathML content is optional 
everything is optional, you don't have to use MathML at all if you don't
want to. I have no idea in what way you mean content
mathml is more optional than presentation mathml.

> and never used in practice.
Maple (for example) uses content mathml when writing out expressions as

> If the MathML
> content definition is by reference to the OM encoding corresponding
> to that MathML content, and is therefore equivalent to a
> subset of OM, then the relationship should be made crystal clear.

MathML isn't _defined_ by reference to OM. But some effort has been made
while defining the two languages to ensure that the definitions are
compatible, and to document the equivalence, I posted a reference to a
document on that topic to this list the other day, There are also some
implementations of the correspondence in XSLT (which aren't complete yet
but will be made available shortly)

> so in fact the OM content in most cases gives
> a big fat hint as to what should be displayed, by choosing
> to transmit only one of the (infinite) number of equivalent
> objects.

There is almost no hint to presentation in the OM encoding.
Neither the layout nor the symbols to be used.

Given your four examples, the natural encoding of

and  a/b

is the same in OM (and in my own translation to Presentation MathML, the choice
of which form to use depends on the context not on the openmath object,
in particular I use the first form if I'm in a display context.

Similarly a*b^(-1) and 


would naturaly be encoded using the same openmath.
In the XSL stylesheets I have for going to presentation there are some
fairly ad hoc rules about when to use a visible and when to use an
invisible times, which you get depends on the values of a and b, not on
the operator used for multiplication.

For example you get ab and 3b but a \times 3 and 3 \times 4, so the choice of
presentation form for the multiplication operator depends on its
arguments not on the operator. This logic is most certainly only encoded
in that one particular stylesheet it is not at all part of the OM

> Just that if you stated that MathML is a subset of OM
> you would not have to distinguish them.

But we didn't, so we do.

> You don't even know what OM is competing with.

The fact that there are many possible methods of encoding mathematics is
the main reason for OpenMath. It does not mean that it is competing with
any of those systems, it is just offered as a possible common ground.

> It would provide a review outside the OM club.

perhaps, but there are other priorities at present. The document is
available in public so anyone is free to comment on it.

> It would mean that you could use the word "standard"
> with the same technical connotation as
> "ANSI Standard" C, Common Lisp, ...  or

Yes, ANSI, being the US representative at ISO, standards have a different
legal status. But getting anything through ISO is time consuming (even
if successful) and as I say it isn't clearly a good use of time at present.

> "IEEE Standard" binary floating point arithmetic ...
My understanding is that IEEE is a consortium and its standards don't
have any different legal status than any other body do they? 


This message has been checked for all known viruses by Star Internet
delivered through the MessageLabs Virus Scanning Service. For further
information visit http://www.star.net.uk/stats.asp or alternatively call
Star Internet for details on the Virus Scanning Service.
om at openmath.org  -  general discussion on OpenMath
Post public announcements to om-announce at openmath.org
Automatic list maintenance software at majordomo at openmath.org
Mail om-owner at openmath.org for assistance with any problems

More information about the Om mailing list