cdm/src/main/java/ucar/nc2/ft/point/standard/Evaluator.java
static public String getLiteral(NetcdfDataset ds, String key, Formatter errlog) {
    if (key.startsWith(":")) {
      String val = ds.findAttValueIgnoreCase(null, key.substring(1), null);
      if ((val == null) && (errlog != null))
        errlog.format(" Cant find global attribute %s%n", key);
      return val;
    }

    return key;
  }
static public String getLiteral(NetcdfDataset ds, String key, Formatter errlog) {
    if (key.startsWith(":")) {
      String val = ds.findAttValueIgnoreCase(null, key.substring(1), null);
      if ((val == null) && (errlog != null))
        errlog.format(" Cant find global attribute %s%n", key);
      return val;
    }

    return key;
  }
Translate key to value

@param ds     search in this dataset
@param key    if starts with ":", search for global attribute
@param errlog error messages here
@return return global attribute value or the key itself