Comment describing your root element Index for non sequential data access Offset of the element identified by name (index attribute) and id This is a unique identifier for the elements of type "name" present in the index (e.g.: for an element of type scan, this will be the scan number) name of the element the index entries are pointing to (e.g: scan) offset of the index element (if 0 no index present) sha-1 sum for this file (from the beginning of the file up to (and including) the opening tag of sha1