I am not sure what exactly you want ot achive.There is a mergeLayers
option which would merge setting to 'true' all layers in the result, by
setting to 'false' retain the layers.false (default) - Layers from
different source documents are kept distinct in the assembled document.
If the layerLabel attribute in the source document is specified, the
names are modified by the label; otherwise, the layers keep the same
names.rgsDieter