How do you declare multiple specific capacitances on one cell in NeuroML?

Generally, specific capacitance is declared in the biophysicalProperties section and applies to the whole cell. For example:

<biophysicalProperties id="biophys">
    <membraneProperties>
        ...
        <specificCapacitance value="1.0 uF_per_cm2"/>
        ...
    </membraneProperties>
    <intracellularProperties>
        ...
    </intracellularProperties>
</biophysicalProperties>

How can I assign a different value of the specific capacitance to different parts of the cell? E.g. one value for the soma and another for the dendrites.

You can assign a different specific capacitance values to different segment groups of the cell as follows:

<specificCapacitance segmentGroup="soma_group"     value="1.0 uF_per_cm2"/>
<specificCapacitance segmentGroup="dendrite_group" value="4.0 uF_per_cm2"/>