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D.4.9 The faceting Element

Parent: graph
Contents: cross layer*

The faceting element describes the row, column, and layer structure of the table. Its cross child determines the row and column structure, and each layer child (if any) represents a layer.

faceting has no attributes (other than id).

The cross Element

Parent: faceting
Contents: nest nest

The cross element describes the row and column structure of the table. It has exactly two nest children, the first of which describes the table’s rows and the second the table’s columns.

cross has no attributes (other than id).

The nest Element

Parent: cross
Contents: variableReference+

A given nest usually consists of one or more dimensions, each of which is represented by variableReference child elements. Minimally, a dimension has two variableReference children, one for the categories, one for the data, e.g.:

<nest>
  <variableReference ref="dimension0categories"/>
  <variableReference ref="dimension0"/>
</nest>

Groups of categories introduce additional variable references, e.g.

<nest>
  <variableReference ref="dimension0categories"/>
  <variableReference ref="dimension0group0"/>
  <variableReference ref="dimension0"/>
</nest>

Grouping can be hierarchical, e.g.

<nest>
  <variableReference ref="dimension0categories"/>
  <variableReference ref="dimension0group1"/>
  <variableReference ref="dimension0group0"/>
  <variableReference ref="dimension0"/>
</nest>

XXX what are group maps?

<nest id="nest_1973">
  <variableReference ref="dimension1categories"/>
  <variableReference ref="dimension1group1map"/>
  <variableReference ref="dimension1group0map"/>
  <variableReference ref="dimension1"/>
</nest>
<nest>
  <variableReference ref="dimension0categories"/>
  <variableReference ref="dimension0group0map"/>
  <variableReference ref="dimension0"/>
</nest>

A nest can contain multiple dimensions:

<nest>
  <variableReference ref="dimension1categories"/>
  <variableReference ref="dimension1group0"/>
  <variableReference ref="dimension1"/>
  <variableReference ref="dimension0categories"/>
  <variableReference ref="dimension0"/>
</nest>

One nest within a given cross may have no dimensions, in which case it still has one variableReference child, which references a derivedVariable whose value attribute is constant(0). In the corpus, such a derivedVariable has row or column, respectively, as its id.

nest has no attributes (other than id).

The variableReference Element

Parent: nest
Contents: empty

variableReference has one attribute.

Required: ref

The id of a sourceVariable or derivedVariable element.

The layer Element

Parent: faceting
Contents: empty

Each layer is represented by a pair of layer elements. The first of this pair is for a category variable, the second for the data variable, e.g.:

<layer value="0" variable="dimension0categories" visible="true"/>
<layer value="dimension0" variable="dimension0" visible="false"/>

layer has the following attributes.

Required: variable

The id of a sourceVariable or derivedVariable element.

Required: value

The value to select. For a category variable, this is always 0; for a data variable, it is the same as the variable attribute.

Optional: visible

Whether the layer is visible. Generally, category layers are visible and data layers are not, but sometimes this attribute is omitted.

Optional: method

When present, this is always nest.


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