Meta data


Datalad has built-in, modular, and extensible support for meta data in various formats. The core concept is that meta data is accessed via dedicated parsers in their native format, avoiding the need for mandatory conversion into a “standard” format. Via these parser datalad is capable of performing a certain amount of meta data homogenization, and standardization into a JSON-LD compliant linked data structure for the purpose of meta data aggregation in superdatasets. Through this mechanism it is possible to obtain and query meta data of any number of subdatasets without the need to actually install them.

Sample datasets with meta data superdataset contains a collection of datasets which we have prepared primarily from available online data resources such as OpenfMRI, CRCNS, etc. Many of those datasets came with meta data in their native formats, such as Brain Imaging Data Structure (BIDS). DataLad has aggregated metadata where it was available to enable basic search queries. If you run search command outside of any datalad dataset, it will offer to install our superdataset at ~/datalad and then search through its metadata. If that superdataset is already installed (by datalad search or manually via datalad install -s /// ~/datalad), you can refer to it in the search command using -d /// option, e.g.:

$> datalad search -d /// bids
..    .

Supported meta data formats

This following sections provide an overview of supported meta data formats.

RFC822-compliant meta data

This is a custom meta data format, inspired by the standard used for Debian software packages that is particularly suited for manual entry. This format is a good choice when meta data describing a dataset as a whole cannot be obtained from some other structured format. The syntax is RFC 822-compliant. In other words: this is a text-based format that uses the syntax of email headers. Meta data must be placed in DATASETROOT/.datalad/meta.rfc822 for this format.

Here is an example:

Name: myamazingdataset
Version: 1.0.0-rc3
Description: Basic summary
 A text with arbitrary length and content that can span multiple
 paragraphs (this is a new one)
License: CC0
 The person who associated a work with this deed has dedicated the work to the
 public domain by waiving all of his or her rights to the work worldwide under
 copyright law, including all related and neighboring rights, to the extent
 allowed by law.
 You can copy, modify, distribute and perform the work, even for commercial
 purposes, all without asking permission.
Funding: Grandma's and Grandpa's support
Cite-As: Mike Author (2016). We made it. The breakthrough journal of unlikely
  events. 1, 23-453.
DOI: 10.0000/nothere.48421

The following fields are supported:

A description of the target audience of the dataset.
A comma-delimited list of authors of the dataset, preferably in the format. Firstname Lastname <Email Adress>
Instructions on how to cite the dataset, or a structured citation.
Description of the dataset as a whole. The first line should represent a compact short description with no more than 6-8 words.
A digital object identifier for the dataset.
Information on potential funding for the creation of the dataset and/or its content. This field can also be used to acknowledge non-monetary support.
A URL to a project website for the dataset.
A URL to an issue tracker where known problems are documented and/or new reports can be submitted.
A description of the license or terms of use for the dataset. The first lines should contain a list of license labels (e.g. CC0, PPDL) for standard licenses, if possible. Full license texts or term descriptions can be included.
Can be used in addition and analog to Author, when authors (creators of the data) need to be distinguished from maintainers of the dataset.
A short name for the dataset. It may be beneficial to avoid special characters, umlauts, spaces, etc. to enable widespread use of this name for URL, catalog keys, etc. in unmodified form.
A version for the dataset. This should be in a format that is alphanumerically sortable and lead to a “greater” version for an update of a dataset.

Brain Imaging Data Structure (BIDS)

Datalad has basic support for extraction of meta data from the BIDS dataset_description.json file.

Friction-less data packages

Datalad has basic support for extraction of meta data from friction-less data packages (datapackage.json). file.

JSON-LD meta data format

Datalad uses JSON-LD as its primary meta data format. By default, the following context (available from here is used for any meta data item:

  "@context": {
    "@vocab": "",
    "doap": "",
    "Author": {"@id": "schema:author"},
    "Audience": {"@id": "doap:audience"},
    "Citation": {"@id": "schema:citation"},
    "Contributors": {"@id": "schema:contributor"},
    "Description": {"@id": "schema:description"},
    "Homepage": {"@id": "doap:homepage"},
    "IssueTracker": {"@id": "doap:bug-database"},
    "Keywords": {"@id": "schema:keywords"},
    "License": {"@id": ""},
    "Location": {"@id": "schema:location"},
    "Maintainer": {"@id": "doap:maintainer"},
    "Name": {"@id": "schema:name"},
    "ShortDescription": {"@id": "doap:shortdesc"},
    "Type": {"@id": "schema:type"},
    "Version": {"@id": "doap:Version"},
    "conformsTo": {"@id": "dcterms:conformsTo"},
    "fundedBy": {"@id": "foaf:fundedBy"},
    "hasPart": {"@id": "dcterms:hasPart"},
    "isPartOf": {"@id": "dcterms:isPartOf"},
    "isVersionOf": {"@id": "dcterms:isVersionOf"},
    "modified": {"@id": "dcterms:modified"},
    "sameAs": {"@id": "schema:sameAs"}

While it is technically possible to mix different contexts across items this has not been fully tested yet.

The following sections describe details and changes in the meta data specifications implemented in datalad.


  • Original implementation