> For the complete documentation index, see [llms.txt](https://mhealth-specification.gitbook.io/mhealth-specification/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mhealth-specification.gitbook.io/mhealth-specification/directory-structure/overview.md).

# Overview of directory structure

Description of the directory structure of a typical mhealth storage compatible dataset

```
- root
 - [Participant ID 1]
     - MasterSynced
     - OriginalRaw
     - Derived
         - [SetName]
     - Meta
         - location_mapping.csv
         - subject.csv
         - sessions.csv
 - [Participant ID 2]
     - MasterSynced
     - OriginalRaw
     - Derived
         - location_mapping.csv
         - subject.csv
         - sessions.csv
         - [SetName]
 - MetaCrossParticipants
     - location_mapping.csv
     - sessions.csv
     - subjects.csv
 - DerivedCrossParticipants
     - [SetName]
```

## Participant ID

1. Allowed characters: *alphabets* and *digits*.
2. Globally Unique.
3. Used as directory name.

### MasterSynced

1. Synchronized **sensor**, **feature**, **event**, **annotation** files, stored in mhealth storage format.
2. Files are divided **hourly**, in folder `MasterSynced/YYYY/MM/DD/HH/`

### OriginalRaw

1. Original files stored in manufacturer's format.
2. Arbitrary directory structure.
3. Recommended to divide sub directories by the type of sensor or data.

### Meta

1. Store meta files that are additional information to files in `MasterSynced`folder.
2. Meta files should be kept unchanged all the time.

### Derived

1. Store data files derived or merged from files in `MasterSynced` folder. Such as **feature** files, **class** files, **model** files, ema summary files.
2. `SetName` is used to specify any common properties of a set of derived files. Popular names could be `AllTime`,`LabSession`,`Weekend`, `FebruaryMorning` or the combination between them.

## MetaCrossParticipants

1. Store meta information that is aggregated from files in each participant's  `Meta` folders.
2. Meta information is the unchanged information for a dataset.

## DerivedCrossParticipants

1. Store data files derived and merged from files in each participant's `MasterSynced` or `Derived` folders.
2. `SetName` is used to specify the time or participant characte of a set of derived files. For example, `AllTimeMale`, `LabSessionAdults` and so on.