The campaign feature allows for data to be collected by "forms" that have defined data fields (See CampaignCreate, CampignList, CampaignDelete.) The FormData function allows the collected data, or "responses" to be retrieved.
Each response has a sequence number and a status, which may be "new" or "old" (also referred to as "deleted").
Responses may be collected over an extended period of time, and there may be many of them. The FormData function has features that allow for the selection of responses based on their modification time, status, or sequence number, so it can be called repeatedly to update the set of responses that have already been retrieved. Additionally, the size of the result can be limited to a specified number of records, which can protect the user from an unmanageably large response.