MathML for complex number expressions

I am attempting to write a program which will generate MathML 
from algebraic expressions.  The problem is when working on 
complex expressions, when is the type= information needed.

For example, for z = (1,2)

<declare type="complex-cartesian">
<ci>z</ci>
<cn>1</cn>
<sep/>
<cn>2</cn>
</declare>

Is this correct or should the type be repeated in the first <cn> ?

and for z = (x,y)

<declare type="complex-cartesian">
<ci>z</ci>
<ci>x</ci>
<sep/>
<ci>y</ci>
</declare>

Here if I repeated the type in the <ci> for x it would imply that x is 
complex which is not what I want.

Please point me to some examples, as I can't find these points 
answered in the definition statement.

Thanks

John Fletcher

-------------------------------------------------------------------
Dr John P. Fletcher          Tel: (44) 121 359 3611 ext 4625
Chemical Engineering and Applied Chemistry (CEAC),
School of Engineering and Applied Science (SEAS),
Aston University,            Fax: (44) 121 359 4094
Aston Triangle,              Email: J.P.Fletcher@aston.ac.uk
BIRMINGHAM B4 7ET  U.K.      CEAC Web site http://www.ceac.aston.ac.uk/

Received on Friday, 7 December 2001 03:53:51 UTC