The ID statement specifies SAS variables containing values for pre- and post-optimal processing and analysis. These variables are not processed by PROC INTPOINT but are read by the procedure and written in the CONOUT= data set. For example, imagine a network used to model a distribution system. The SAS variables listed on the ID statement can contain information on the type of vehicle, the transportation mode, the condition of the road, the time to complete the journey, the name of the driver, or other ancillary information useful for report writing or describing facets of the operation that do not have bearing on the optimization. The ID variables can be character, numeric, or both.

If no ID list is specified, the procedure forms an ID list of all SAS variables not included in any other implicit or explicit list specification. If the ID list is specified, any SAS variables in the ARCDATA= data set not in any list are dropped and do not appear in the CONOUT= data set.