Unit validation is giving incorrect warnings

[fbergmann]

The attached model model gives a validation warning because of an issue with the time unit:

Warning Line 155 Column 20: (SBML Validation Rule #10541) The units of the 'math' formula in a definition are expected to be the equivalent of substance per time. Reference: L2V4 Section 4.13.5 Expected units are mole (exponent = 1, multiplier = 1, scale = -9), second (exponent = -1, multiplier = 1, scale = -3) but the units returned by the $expression\; in\; the(from\; thewith\; id\; \text{'}R1\text{'})\; are\; second\; (exponent\; =\; -1,\; multiplier\; =\; 0.0001,\; scale\; =\; 0),\; mole\; (exponent\; =\; 1,\; multiplier\; =\; 1,\; scale\; =\; -9).$

Somehow the multiplier is used instead of the scale.

[skeating]

actually the reason why it gives the error is that the units are wrong:

`

       <minus/>

            <apply>

              <times/>

              <ci> kf_R1 </ci>  <!--one_over_nM_ms-->

              <ci> gaba </ci>   <!--substance-->

              <ci> GABABR </ci> <!--substance-->

            </apply>

            <apply>

              <times/>

              <ci> kr_R1 </ci>      <!--one_over_nM_ms-->

              <ci> gabaGABABR </ci> <!--substance-->

            </apply>

          </apply>

`

is trying to subtract a unit that is time x substance from a unit that is time x substance x substance

[fbergmann]

@skeating for me kr_R1 has the unit one_over_ms, so it is different. Since we have

      <unitDefinition id="one_over_ms">
        <listOfUnits>
          <unit kind="dimensionless" exponent="1" scale="0" multiplier="1"/>
          <unit kind="second" exponent="-1" scale="-3" multiplier="1"/>
        </listOfUnits>
      </unitDefinition>
      <unitDefinition id="one_over_nM_ms">
        <listOfUnits>
          <unit kind="dimensionless" exponent="1" scale="0" multiplier="1"/>
          <unit kind="mole" exponent="-1" scale="-9" multiplier="1"/>
          <unit kind="litre" exponent="1" scale="1" multiplier="1"/>
          <unit kind="second" exponent="-1" scale="-3" multiplier="1"/>
        </listOfUnits>
      </unitDefinition>

regardless, does this explain the issue for you?

[skeating]

you still cannot subtract something with units AB from something with units ABB

[fbergmann]

Stefan found the issue. since volume and liter are defined with a scale=0, then the litre component in the one_over_nM_ms unit should also have a scale=0. If that is corrected, then the validator does not complain anymore either.

[skeating]

yes it was trying to subtract two different units!!