The two ways users can do longitudinal data collection in Magpi are:
1 - flat form with ID — each respondent is assigned a unique ID. When it is time to gather new data, the interviewer conducts the interview and enters the respondents unique ID. The interviewer in this case does not need to see previous data and is just collecting a subsequent data point. Example: successive growth measurements in a child population, or successive rainfall measurements at each collection apparatus, etc. The longitudinal aspect of the data is accessible to data managers, who can see all collected data.
2 - form + subform — in this case a main form is constructed with the unchanging elements (e.g. name, ID, DOB, etc), with a subform called, for example, “encounter”. At each visit, a new subform record is added, while previous encounter records are visible to the interviewer as needed. More on subforms: https://support.magpi.com/support/solutions/articles/4902-using-subforms-pro-enterprise-users-
The approach taken depends on whether it is necessary for the data collector to have access to previous visit data. Both approaches are used widely within Magpi.