The REFERENCE data structure is designed to represent initial input parameters used in population modeling. This structure is new to both CDISC and stakeholders. At present, this structure will be restricted to TIG v1.0 and withheld from an associated version of ADaM to allow time for stakeholders to use the standard in practice. Experience with this standard will inform subsequent refinements if needed. The standards and refinements, if any, will be incorporated into the next version of the TIG and the associated version of ADaM.