Table 2.
Data sources and their properties.
| Data Source | Description | Android | iOS | Optional |
|---|---|---|---|---|
| Applications usage | application category and duration of usage | event-based | - | no |
| Calendar | total number of calendar events | 4 h | 4 h | no |
| Call log | number and duration of incoming, outgoing, missed calls | event-based | event-based | no |
| Camera | cropped face images | event-based | event-based | yes |
| GPS | latitude and longitude | 15 min | 15 min | no |
| Gravity | magnitude of gravity in x, y and z directions | 15 min | 15 min | no |
| Keystroke log | number of key presses, backspaces, auto-correction, typing duration, and number of unique applications | event-based | - | no |
| Light | illuminance in lux | 15 min | - | no |
| Microphone | sound energy and pitch | 15 min | event-based | yes |
| Music | song title and artist name | event-based | - | no |
| Notifications | notification event, click-through rate, and decision time | event-based | - | no |
| Pedometer | number of steps | event-based | event-based | no |
| Physical activity | duration of still, walking, running, cycling, being in vehicle activities | event-based | event-based | no |
| Screen | duration of unlocked screen state | event-based | event-based | no |
| Significant motion | number of events when sudden motion occurs | event-based | event-based | no |
| Social Networking Service (SNS) | social media metrics (e.g., number of followers and posts) | 24 h | - | yes |
| Stored media | number of images stored | 4 h | 4 h | yes |
| Short Messaging Service (SMS) | number of characters in incoming text messages | event-based | - | no |
| Wi-Fi | number of nearby access points | 30 min | - | no |