pdaLayerPurpose
An optional attribute is type which can have one of the following values: passive, active, doc, misc, metal, metalalt, metalrouting, metal1, metal2, metal3, metal4, metal5, metal6, metal7, metal8, metal9, rf, rf_gsg, rf_gssg, rf_s, rf_g.Metal1-9 are for multi-layer metal, with '1' being closes to the photonics; moving up to higher numbers is typically done with VIA's.
Structure
This element does not have elements. The attributes are shown below, in a sorted per type fashion.<purpose type="..." ... > ... </purpose>
XSD The schema file can be downloaded or viewed at xPDK_Base.