MIL-PRF-32118, PERFORMANCE SPECIFICATION, VECTOR PRODUCT FORMAT (VPF) DATABASE UPDATE (VDU) (20 MAR 2003)., This specification defines requirements for the National Imagery and Mapping Agency's (NIMA) Vector Product Format (VPF) Database Update (VDU). This specification further defines the tables that are necessary to build an "update layer" for NIMA Vector Product Format (VPF) data sets that require tracking and accountability for changes made to the underlying VPF data set.