+-- |The name of the RRD you want to create. RRD files should end with
+-- the extension @.rrd@. However, RRDtool will accept any filename.
+newtype RRDPath = RRDPath FilePath
+
+-- |Do not clobber an existing file of the same name.
+data KeepOldRRD = KeepOldRRD
+
+-- |Specifies the time in seconds since @1970-01-01 UTC@ when the
+-- first value should be added to the RRD. RRDtool will not accept any
+-- data timed before or at the time specified. (default: @now - 10s@)
+newtype RRDStartTime = RRDStartTime POSIXTime
+
+-- |Specifies the base interval in seconds with which data will be fed
+-- into the RRD. (default: 300 sec)
+newtype RRDInterval = RRDInterval NominalDiffTime
+
+class RRDSpec s
+instance ( HOccurs RRDPath s
+ , HOccursOpt KeepOldRRD s
+ , HOccursOpt RRDStartTime s
+ , HOccursOpt RRDInterval s
+ )
+ => RRDSpec s
+