New SBML units attribute on MathML cn element
An idea that has been thrown around in the past is to provide the ability to attach units to numbers in MathML using an attribute codesbml:units/code. It would look like this example:
<math xmlns="http://www.w3.org/1998/Math/MathML" xmlns:sbml="http://www.sbml.org/sbml/level3/version1/core"> <apply> <times/> <cn sbml:units="dimensionless"> 5 </cn> <ci> x </ci> </apply> </math>
This is an approach pioneered by CellML. The SBML Editors have been revisiting this issue, and actually, we now think there is no really compelling reason not to adopt this approach for SBML L3. It would certainly make it easier to add units on numbers in models.
One small matter is that the XML namespace prefix (whether called
sbml or something else in a given model) would have to be declared somewhere in the XML document. However, this can be done in any of several places, such as in the
<sbml> element or the
<math> element or even on the
<cn> element itself.