## 5 The Recordings  
This section details how recordings generated by the two applications are organized and how they can be accessed. As introduced in Section 3.2, both the applications have a main folder in the public storage of the smartphone: AAL - Acquisition for the application that acquires the signals from the sensors, and AAL - Labeling for the application that labels these data. Because these files are in public storage, a user can access them in an easy way either by connecting the smartphone to a computer or directly from the mobile device. As shown in Figure 6, both the AAL - Acquisition folder and AAL - Labeling folder contain two subfolders: configuration and recordings. The configuration folder is discussed in Section 3.2 and contains the files that a user can change in order to adapt the applications according to researchers' needs, while the recordings folder contains the files with the signals and the labels recorded. Figure 5: Screenshots of the labeling application. Each time a subject starts a recording session, the acquisition application creates a new folder whose name is obtained by concatenating the _id_ (identifier) of the subject and the _date and the time_ of the beginning of the recording. For example, the folder subject2_2018-04-09_09:40:21 in Figure 5(a) specifies that the recordings are related to a subject with ID \"subject2\" who recorded a session on April 9, 2018 at 9 am for 40 min and 21 s. Each folder related to an acquisition session performed by a subject contains as many CSV files as the number of sensors that have been selected for the recordings, each of them containing the acquired signals. The name of each file is characterized by an initial string that specifies if the sensor belongs to the smartphone (sp) or to the smartwatch (sw) and is followed by the name of the sensor as provided by the Android API. The files containing signals from smartwatch sensors are transferred to the smartphone via Bluetooth. For example, the file sp-K6 DS3 TRAcceleration Sensor in Figure 5(a) contains the acceleration signals acquired by the sensor identified as K6 DS3 TR hosted in the smartphone. Similarly, the recordings folder of the labeling application contains the data related to the activities performed during application runs. Each time a subject starts to label his/her first activity, the labeling application creates a new folder following the same pattern of the acquisition application. For example, the folder subject2_2018-04-09_09:42:37 in Figure 5(b) specifies that the labels are related to a subject with ID \"subject2\" who recorded a session on April 9, 2018 at 9 am for 42 min and 37 s. Each folder related to a labeling session contains a CSV file named labeling that contains the labels of the activities that the subject has performed (see Figure 5(b)). The subfolders of the acquisition application recordings folder can be associated to the corresponding subfolders of the labeling application recordings folder because of the names assigned to the subfolders. That is, given a recordings subfolder in the acquisition application, the associated subfolder in the labeling application is that which has the same identifier for the subject and a time that is the closest to that of the acquisition subfolder. For example, the subfolder subject2_2018-04-09_09:40:21 created by the acquisition application and the subfolder subject2_2018-04-09_09:42:37 created by the labeling application can be associated because they have the same identifier and because the date of the subfolder in the labeling application is the closest to that of the folder in the acquisition application. Figure 6: The folder organization in the acquisition application (**a**), and the folder organization in the labeling application (**b**). Figure 7a,b show respectively the fragments of the sp-K6 DS3 TR Acceleration Sensor and sw-BM1383 GLV Pressure Sensor files stored in the subject_2_2018-04-09_09:40:21 folder.