This is an example of a definition for a dot density theme:
<FeatureLayer id="id5" name="USA" alias="USA" volatile="unknown">
<DataSourceRef ref="id4"/>
<FeatureStyleModifierThemeList>
<FeatureStyleDensityTheme id="id6" alias="Dot Density Theme id6" name="Dot Density with Pop_1990">
<DensityValueExpression>
<NumericValueExpression>
<AttributeName>Pop_1990</AttributeName>
</NumericValueExpression>
</DensityValueExpression>
<ValuePerDot>600000</ValuePerDot>
<DotStyle>
<PointStyle>
<FontSymbol text=""" size="4" size-unit="mapinfo:length pt" stroke="rgb(255,0,0)" stroke-opacity="1" family="MapInfo 3.0 Compatible"/>
</PointStyle>
</DotStyle>
</FeatureStyleDensityTheme>
</FeatureStyleModifierThemeList>
</FeatureLayer>