#' @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.