Underlay

Underlay is a synonym for Structure and is the deserialized data from the source. As such it is the content of a Document as created by the Document Factory.

This virtual layer is closest to the source and has not been modified by any layer. However, it is possible that the Document System has modified the source in order to create the underlay. These modifications are not visible to Black Fennec and will most likely be lost when the data is saved.