"get.metadata" <-
function(meta,useHead=NULL,filters=NULL,include=NULL,exclude=NULL)
  {
    if(!is.null(useHead) && (!is.character(useHead) || (length(useHead)==0)))
      stop("Header must be either NULL or of type non-empty character")
    if(!is.null(filters) && (!is.list(filters) || (length(filters)==0) || !is.character(unlist(filters)) || is.null(names(filters))))
      stop("Filters must be either NULL or of type non-empty tagged character list")
    if(!is.null(include) && (!is.character(include) || (length(include)==0)))
      stop("Include must be either NULL or of type non-empty character")
    if(!is.null(exclude) && (!is.character(exclude) || (length(exclude)==0)))
      stop("Exclude must be either NULL or of type non-empty character")
    
    meta <- unlist(meta)
    if(is.null(meta) || is.na(meta))
      return(as.character(NA))
    mInds <- 1:length(meta)
    mIndsMatch <- rep(TRUE,length(mInds))
    if(!is.null(useHead)) {
      mInds <- mInds[grep(useHead,names(meta))]
      mIndsMatch <- mIndsMatch[mInds]
      if(!is.null(filters)) {
        for(i in 1:length(filters)) {
          fInds <- grep(names(filters[i]),names(meta))
          fIndsMatch <- (meta[fInds]%in%unlist(filters[i]))
          mIndsMatch <- mIndsMatch & fIndsMatch
        }
      }
    }
    meta <- as.list(as.character(meta[mInds[mIndsMatch]]))
    meta <- lapply(meta,remove.meta.chars)
    meta <- unique(unlist(meta))
    if(is.null(meta))
      return(as.character(NA))
    if(!is.null(include))
      meta <- meta[meta %in% include]
    if(!is.null(exclude))
      meta <- meta[!(meta %in% exclude)]
    if(length(meta)==0)
      return(as.character(NA))
    return(meta)
  }