xPDK Interim (application) layer

It is often handy for more complex (boolean) operations to have some "gds" layers that are not actually written to GDS files, but are just used by the application to save repeated work. Allowing the use of such interim layers simplifies the layer operation definitions also as they do not need to be recursive and repeated.
In addition to their use in boolean operations, the same aspects often holds for more complex geometrical design rule checks.

The fields for an applayer are almost the same as for a layer (see GDS Layer), but it does not have the gds_number, gds_datatype, polarity and masksupplier as the output should not go to file.
The documentation on the other fields is the same and is not repeated here.

Simple example

The following example shows a very minimal set, which is ok, but lacks the information like purpose or doc to be easy to maintain in the longer run.
full file

 <!-- some output layers for interim results -->
<applayer name="layerA0"/>
<applayer name="layerA1"/>
<applayer name="layerA2"/>
This example shows it very shortly, but it is recommended to document the purpose of the interim layer for future understanding / new colleques. This is done in the next example with the layerAnyData where both the purpose and doc are used (see GDS layer for details).

More realistic example

An example that uses the layerOr to merge data for a possible “data in cell area” test can be written this way. It uses the SingleLayerOps field layerOr (see single layer operations) instead of a series of the multi-layer versions.
full file

 <!-- some real layers for interim results -->
<layer name="layer0">
 <gds_number>0</gds_number> <gds_datatype>0</gds_datatype>

<layer name="layer1">
 <gds_number>1</gds_number> <gds_datatype>0</gds_datatype>

<layer name="layer2">
 <gds_number>2</gds_number> <gds_datatype>0</gds_datatype>

<applayer name="layerAnyData">
 <purpose>Join of data layers</purpose>
 <doc>This join is intended for a "data inside chip area" design
      rule test.