If the changing HMIS structures are not adequately managed by the SAPHMIS, the longitudinal use of the reported data can not be granted. But longitudinal comparison of certain variables are one especially useful feature of a monitoring system for health services. E.g. for diseases with a strong seasonal dependency it might be especially interesting to compare the number of cases seen in one month with the number of cases seen in the same month of the previous years.

For the SAPHMIS this means, that it has to keep track of the changes in the HMIS. If the values of a certain variable are being retrieved for a report at one point of time t and for a previous point of time t-1, the SAPHMIS has to recognize structural changes of the HMIS in between t and t-1 for the presentation of data and the calculation of indicators.