For Chart visualization, we can start from exporting the chart from dynamics CRM and then Analyzing the contents of "Visualizations" in customization.xml.
What you see in "Visualization" is that output that you will get from fetching a record of "savedqueryvisualization".
Within Visualization Tag there is all data that is required to generate the chart.
Information you are looking for is available in DataDescription and PresentationDescription section of the chart.
Value of DataDescription
<datadefinition>
<fetchcollection>
<fetch mapping="logical" aggregate="true">
<entity name="incident">
<attribute alias="aggregate_column" name="incidentid" aggregate="count" />
<attribute groupby="true" alias="groupby_column" name="ownerid" />
<attribute groupby="true" alias="groupby_priority" name="prioritycode" />
</entity>
</fetch>
</fetchcollection>
<categorycollection>
<category>
<measurecollection>
<measure alias="aggregate_column" />
</measurecollection>
</category>
</categorycollection>
</datadefinition>
Value of PresentationDescription
<Chart Palette="None" PaletteCustomColors="91,151,213; 237,125,49; 160,116,166; 255,192,0; 68,114,196; 112,173,71; 37,94,145; 158,72,14; 117,55,125; 153,115,0; 38,68,120; 67,104,43; 124,175,221; 241,151,90; 186,144,192; 255,205,51; 105,142,208; 140,193,104; 50,125,194; 210,96,18; 150,83,159; 204,154,0; 51,90,161; 90,138,57;">
<Series>
<Series ChartType="StackedColumn" Font="{0}, 9.5px" LabelForeColor="59, 59, 59" CustomProperties="PointWidth=0.75, MaxPixelPointWidth=40"></Series>
</Series>
<ChartAreas>
<ChartArea BorderColor="White" BorderDashStyle='Solid'>
<AxisY LabelAutoFitMinFontSize="8" TitleForeColor="59, 59, 59" TitleFont="{0}, 10.5px" LineColor="165, 172, 181" IntervalAutoMode="VariableCount">
<MajorGrid LineColor="239, 242, 246" />
<MajorTickMark LineColor="165, 172, 181" />
<LabelStyle Font="{0}, 10.5px" ForeColor="59, 59, 59" />
</AxisY>
<AxisX LabelAutoFitMinFontSize="8" TitleForeColor="59, 59, 59" TitleFont="{0}, 10.5px" LineColor="165, 172, 181" IntervalAutoMode="VariableCount">
<MajorGrid Enabled="False" />
<MajorTickMark Enabled="False" />
<LabelStyle Font="{0}, 10.5px" ForeColor="59, 59, 59" />
</AxisX>
</ChartArea>
</ChartAreas>
<Titles>
<Title Alignment="TopLeft" DockingOffset="-3" Font="{0}, 13px" ForeColor="0, 0, 0"></Title>
</Titles>
</Chart>
Retrieval Logic: (Data Description)
Fetch XML -> You will not get the data from "savedqueryvisualization" entity but only the logic to retrieve data.
You can use FetchXML within Datadescription and make another call to get data.
Axis Data Logic: (DataDescription)
GroupBy Column -> Used in Sequence they appear in Fetch XML
Aggregated Column -> Displayed in Count Axis
Layout of X-Axis vs Y-Axis: (Presentation Description)
Its defined by Chart Type
PieChart -> No Axis
Column, Stacked Column -> Count is Y-Axis
Bar, StackedBar -> Count is X-Axis.