ISO 19115 Metadata Maintenance
The ISO Metadata Standard uses the same object to describe the maintenance of data (resourceMaintenance) and metadata (metadataMaintenance). This object describes who updates what and how frequently. The who is described by a CI_Responsibility and the frequency is described by the MD_MaintenanceFrequencyCode code list or by the userDefinedMaintenanceFrequency.
The MD_MaintenanceFrequencyCode code list was probably the most awkward code list in ISO 19115 because resources and metadata are updated on many different schedules and is impossible to represent all of these in a reasonable code list. Fortunately, the MD_Maintenance object also includes a userDefinedMaintenanceFrequency which can be any ISO 8601 compliant duration. The MD_MaintenanceFrequencyCode was required in 19115. It is changed to optional in the current version (19115-1).
The what element is described using a MD_Scope that includes a MD_ScopeCode and MD_ScopeDescription. The MD_ScopeCode is a code list that gives a general indication of which elements of the dataset are being maintained. The MD_ScopeDescription gives more details about those elements. For example, if the MD_ScopeCode were "software", the MD_ScopeDescription/other could be used to describe specifically what software maintenance occurred.