BIDS Validation

NEMAR requires all datasets to be in valid BIDS format. This guide covers validation.

Quick Validation

nemar dataset validate ./my-dataset

What Gets Checked

The BIDS validator checks:

Structure - Files and folders follow BIDS naming conventions
Metadata - Required JSON sidecar files are present
Consistency - Data matches metadata descriptions
Completeness - Required files exist

Understanding Results

Errors (Must Fix)

Errors indicate invalid BIDS structure that must be fixed:

[ERROR] dataset_description.json is missing
[ERROR] Invalid JSON in participants.tsv

Warnings (Review)

Warnings suggest potential issues but don’t block upload:

[WARNING] Recommended field 'License' is missing
[WARNING] No README file found

Validation Options

# Basic validation
nemar dataset validate ./my-dataset

# Verbose output (show all checks)
nemar dataset validate ./my-dataset --verbose

# Ignore specific warnings
nemar dataset validate ./my-dataset --config .bidsvalidatorrc

# Output as JSON
nemar dataset validate ./my-dataset --json

Common Errors and Fixes

Missing dataset_description.json

Create the file in your dataset root:

{
  "Name": "My EEG Dataset",
  "BIDSVersion": "1.9.0",
  "DatasetType": "raw",
  "License": "CC BY-NC 4.0",
  "Authors": ["Last, First", "Last2, First2"]
}

Invalid Filename

BIDS filenames must follow the pattern:

sub-<label>[_ses-<label>][_task-<label>][_run-<index>]_<suffix>.<extension>

Example:

sub-01_ses-01_task-rest_run-01_eeg.edf

Missing Events File

For task data, create an events.tsv:

onset  duration  trial_type
0.0  0.5  stimulus
1.5  0.5  response

Custom Validation Config

Create .bidsvalidatorrc in your dataset root:

{
  "ignore": [
    "/derivatives/"
  ],
  "ignoredFiles": [
    ".DS_Store"
  ]
}

Validation Before Upload

Validation runs automatically during upload. To skip (not recommended):

nemar dataset upload ./my-dataset --skip-validation