Table 2.

Design decisions on the basis of constraints.

Constraint	Design decision
Design to support rapid recall	Rapid recall can be supported through the provision of a reference time frame where users can perform recall by focusing on the time window.
Design for low effort from user	A system that is capable of sending self-report questions as a group of message notifications can allow users to respond on the go, with a single tap on a mobile device. The burden can be further reduced if the group of messages is dependent on the users’ context. For instance, the EMAa system can skip asking about food/drink consumption if the user is physically located in a restaurant when a self-report message group is sent, or the EMA system can provide suggestions for location on the basis of the device’s location to help users avoid searching for an actual address.
Design to capture situations that accompany a behavior	To ensure a response is captured close to a situation, the EMA system should not allow users to respond after a set number of minutes have passed as it is likely the context of the user changes over time. To support this need, participants suggested a 30-min window for capturing responses and context, that is, a notification with a question disappears from the user's screen if the user does not respond within 30 min of receiving the notification.
Design to capture better quantity and quality of data	To maximize data capture, the EMA system can prompt a response at times when the user is awake and does not want to be disturbed. Furthermore, 1 way to personalize this experience for users is to have an onboarding process where the users can set preferences for when they will typically be available to receive EMA questions. Moreover, 1 way to capture data with improved quality, specifically for eating behavior, is to include response options where users can choose the type of food or drink. Similarly, social copresence can also include detailed response choices, which users can prepopulate with their social connections before EMA usage and select those when prompted for social copresence.
Design for user’s safety	A notification can be held back if the EMA system identifies the user is moving in a vehicle. This avoids putting the user in danger.

^aEMA: ecological momentary assessment.