Use this attribute to determine whether this item is an actual zip entry or is one synthesized for part of a real entry's path. A synthesized entry represents a directory within the zip file which has no corresponding entry within the zip file. For example, the entry for the directory foo/ in a zip containing exactly one entry for foo/bar.txt is synthetic. If the zip file contains an actual entry for a directory, this attribute will be false for the nsIZipEntry for that directory. It is impossible for a file to be synthetic. Read only.