#' @slot range Object of class `GRanges`, the genomic ranges of the track items
#' as well as additional annotation information in its `elementMetaData` slot.
#' Please not that the slot is actually implemented as a class union between
#' `GRanges` and IRanges to increase efficiency, for instance for DataTrack
#' objects. This usually does not concern the user.
#' @slot chromosome Object of class `character`, the chromosome on which the
#' track is defined. There can only be a single chromosome for one track. For
#' certain subclasses, the space of allowed chromosome names is limited (e.g.,
#' only those chromosomes that exist for a particular genome). Throughout the
#' package, chromosome name have to be entered either as a single integer scalar
#'  or as a character scalar of the form chrXYZ, where XYZ may be an arbitrary
#'  character string.
#' @slot genome Object of class `character`, the genome for which the track is
#' defined. For most sub-classes this has to be valid UCSC genome identifier,
#' however this may not always be formally checked upon object instantiation.