The structural analysis is the first step in the BSI IT-Grundschutz methodology. You systematically inventory all IT systems, network components, applications, rooms, and communication links within the defined information domain. The result is a complete inventory that serves as the foundation for the protection-requirement assessment and modelling. In an ISO 27001 context the structural analysis corresponds to asset identification. You should keep the structural analysis up to date because it underpins all subsequent security measures.