The asset model is used in ISA/IEC 62443 to represent and describe the relationships and dependencies between different assets in an IACS environment. This model helps organizations identify and document assets, their interconnections, and their significance for operational and cybersecurity purposes. The zone model builds upon the asset model for segmentation, but the asset model itself establishes the foundational relationships.
Reference: ISA/IEC 62443-1-1:2007, Section 4.3.1 ("Asset Model"); Figure 3 ("Example asset model for IACS").