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layout title listed version updated created ietf-keywords author summary
spec
Data Packages
true
1.0.0-beta.17
23 March 2016
12 November 2007
true
Rufus Pollock (Open Knowledge Labs)
Martin Keegan (Open Knowledge Labs)
A Data Package (or DataPackage) is a coherent collection of data and possibly other assets in a single 'package'. It provides the basis for convenient delivery, installation and management of datasets.
NOTE: This is a draft specification - though nearing v1.0. If you have comments or suggestions please file them in the [issue tracker][issues]. If you have explicit changes please fork the [git repo][repo] and submit a pull request.

Changelog

  • 1.0.0-beta.17: make resources property required as per issues #253
  • 1.0.0-beta.16: description is markdown formatted as per issue #152; MimeType for Data Packages is vnd.datapackage issue #245
  • 1.0.0-beta.15: only one of url, path, data present on as per issue #223; remove base property as per issue #232
  • 1.0.0-beta.14: drop licenses in favour of license as per issue #214
  • 1.0.0-beta.13: add support for sharing schemas across resources via schema references as per issue #71
  • 1.0.0-beta.12: remove datapackage_version as per issue #140
  • 1.0.0-beta.11: introduce author, integrate with contributors and remove maintainers and publishers as per this issue
  • 1.0.0-beta.10: license introduced and licenses updated as per this issue
  • 1.0.0-beta.8: last_modified and modified removed following this issue
  • 1.0.0-beta.7: dependencies renamed to dataDependencies following this issue
  • 1.0.0-beta.5 -> 1.0-beta.6: Moved resources from MUST to MAY

Table of Contents

{:.no_toc}

  • Will be replaced with the ToC, excluding the "Contents" header {:toc}

Specification

A data package consists of:

  • Metadata that describes the structure and contents of the package
  • Resources such as data files that form the contents of the package

A valid data package MUST provide a data package "descriptor" file named datapackage.json. This file SHOULD be placed in the top-level directory (relative to any other resources provided as part of the data package).

The data package descriptor provides general metadata about the data package and describes the resources that make up its contents. The structure of the descriptor is specified below.

In addition to this descriptor a data package will include other resources such as data files. The Data Package specification does NOT impose any requirements on their form or structure and can therefore be used for packaging any kind of data.

The data included in the package may be provided as:

  • Files bundled locally with the package descriptor
  • Remote resources, referenced by URL
  • "Inline" data (see below) which is included directly in the datapackage.json file

Illustrative Structure

A minimal data package on disk would be a directory containing a single file:

datapackage.json  # (required) metadata and schemas for this data package

Obviously lacking a single piece of actual data would make this of doubtful use. A slightly less minimal version would be:

datapackage.json
# a data file (CSV in this case)
data.csv

Additional files such as a README, scripts (for processing or analyzing the data) and other material may be provided. By convention scripts go in a scripts directory and thus, a more elaborate data package could look like this:

datapackage.json  # (required) metadata and schemas for this data package
README.md         # (optional) README in markdown format

# data files may go either in data subdirectory or in main directory
mydata.csv
data/otherdata.csv         

# the directory for code scripts - again these can go in the base directory
scripts/my-preparation-script.py

Several exemplar data packages can be found in the datasets organization on github, including:

Descriptor (datapackage.json)

datapackage.json is the central file in a Data Package. It provides:

  • General metadata such as the package's title, license, publisher etc
  • A list of the data "resources" that make up the package including their location on disk or online and other relevant information (including, possibly, schema information about these data resources in a structured form)

The Package descriptor MUST be a valid JSON file. (JSON is defined in RFC 4627).

It MAY contain any number of attributes. All attributes at the first level not otherwise specified here are considered metadata attributes.

A valid descriptor MUST contain a name attribute. These fields, and additional metadata attributes, are described in the "Required Fields" section below.

A valid descriptor MAY contain a resources attribute.

Here is an illustrative example of a datapackage JSON file:

{
  # general "metadata" like title, sources etc
  "name" : "a-unique-human-readable-and-url-usable-identifier",
  "title" : "A nice title",
  "license" : "The package's license",
  "sources" : [...],
  # list of the data resources in this data package
  "resources": [
    {
      ... resource info described below ...
    }
  ],
  # optional
  ... additional information ...
}

Metadata

Required Fields

A valid package MUST include the following fields:

  • name (required) - short url-usable (and preferably human-readable) name of the package. This MUST be lower-case and contain only alphanumeric characters along with ".", "_" or "-" characters. It will function as a unique identifier and therefore SHOULD be unique in relation to any registry in which this package will be deposited (and preferably globally unique).

    The name SHOULD be invariant, meaning that it SHOULD NOT change when a data package is updated, unless the new package version should be considered a distinct package, e.g. due to significant changes in structure or interpretation. Version distinction SHOULD be left to the version field. As a corollary, the name also SHOULD NOT include an indication of time range covered.

  • resources - a JSON array of zero or more JSON objects. Each JSON object describes one of the data resources in the package and MUST follow the specification for resource objects in the "Resource Information" section below.

Strongly Recommended Fields

In addition to the above fields, the following fields SHOULD be included in every package descriptor:

  • license - is a field specifying the license under which the package is provided.

    This property is not legally binding and does not guarantee the package is licensed under the terms defined in this property.

    The object structure MUST contain a type property and a url property linking to the actual text. The type SHOULD be an [Open Definition license ID][od-license] if an ID exists for the license and otherwise may be the general license name or identifier. Here is an example:

      "license": {
    "type": "ODC-PDDL-1.0",
    "url": "http://opendatacommons.org/licenses/pddl/"
  }

Recommended Fields

The following are commonly used fields that the package descriptor MAY contain:

  • title - a title or one sentence description for this package

  • description - a description of the package. The description MUST be markdown formatted -- this also allows for simple plain text as plain text is itself valid markdown. The first paragraph (up to the first double line break) should be usable as summary information for the package.

  • homepage - URL string for the data packages web site

  • version - a version string identifying the version of the package. It should conform to the Semantic Versioning requirements.

  • sources - an array of source objects. Each source object may have name, web and email fields. Example:

    "sources": [{
  "name": "World Bank and OECD",
  "web": "http://data.worldbank.org/indicator/NY.GDP.MKTP.CD"
}]

  • author and contributors - these are fields for describing people or organizations who contributed to this Data Package. author is a single person / organization whilst contributors is an array. By convention, the first contributor is the original author of the package unless author is also present - in this sense, author is simply a convenience that allows for single line entries like the following:

    "author": "Joe Bloggs <joe@bloggs.com>"

    A "person" or "organization" is an object OR string. It MUST contain a name property and MAY contain web and email. An example of the object structure is as follows:

    {
  "name": "Joe Bloggs",
  "email": "joe@bloggs.com",
  "web": "http://www.bloggs.com"
}

    The string version has the following structure:

    NAME <EMAIL> (WEB)

    Example:

    Joe Bloggs <joe@bloggs.com> (http://www.bloggs.com/)

    Email and web are optional in the string version as well e.g.:

    Joe Bloggs
Joe Bloggs <joe@bloggs.com>
Joe Bloggs (http://www.bloggs.com)

    Note on semantics: use of the "author" field does not imply that that person was the original creator of the data in the data package - merely that they created and/or maintain the data package. It is common for data packages to "package" up data from elsewhere. The original origin of the data can be indicated with the sources field - see above.

  • keywords - an Array of string keywords to assist users searching for the package in catalogs.

Optional Fields

A package descriptor MAY contain the following fields:

  • image - a link to an image to use for this data package

  • dataDependencies - Object of prerequisite data packages on which this package depends in order to install. Follows same format as CommonJS Packages spec v1.1.Each dependency defines the lowest compatible MAJOR[.MINOR[.PATCH]] dependency versions (only one per MAJOR version) with which the package has been tested and is assured to work. The version may be a simple version string (see the version property for acceptable forms), or it may be an object group of dependencies which define a set of options, any one of which satisfies the dependency. The ordering of the group is significant and earlier entries have higher priority. Example:

    "dataDependencies": {
   "country-codes": "",
   "unemployment": "2.1",
   "geo-boundaries": {
     "acmecorp-geo-boundaries": ["1.0", "2.0"],
     "othercorp-geo-boundaries": "0.9.8",
   },
}

  • schemas: an Object containing schemas keyed by a name. See the Resource Schemas section below.

NOTE: A Data Package author MAY add any number of additional fields beyond those listed in the specification here. For example, suppose you were storing time series data and want to list the temporal coverage of the data in the Data Package you could add a field `temporal` (cf [Dublin Core][dc-temporal]): 
"temporal": {
  "name": "19th Century",
  "start": "1800-01-01",
  "end": "1899-12-31"
}

This flexibility enables specific communities to extend Data Packages as appropriate for the data they manage. As an example, the Tabular Data Package specification extends Data Package to the case where all the data is tabular and stored in CSV.

Resource Information

Packaged data resources are described in the resources property of the package descriptor. This property is an array of values. Each value describes a single resource and MUST be a JSON object.

Required Fields

Resource information MUST contain one (and only one) of the following attributes which specify the location of the associated data file (either online, 'relative' (local), or 'inline'):

  • url: url of this data resource
  • path: unix-style ('/') relative path to the resource. Path MUST be a relative path, that is relative to the directory or URL in which the descriptor file (datapackage.json) listing this file resides.
  • data: (inline) a field containing the data directly inline in the datapackage.json file. Further details below.
NOTE: the use of a `url` allows a data package to reference data not contained locally in the Data Package. The `path` attribute may also be used for Data Packages located online -- in this case it determines the resource file's URL relative to the `datapackage.json`'s URL.

There are NO other required fields. However, there are a variety of common fields that can be used which we detail below.

Recommended Fields

It is recommended that a resource SHOULD contain the following fields:

  • name: a resource SHOULD contain an name attribute. The name is a simple name or identifier to be used for this resource.

    • If present, the name MUST be unique amongst all resources in this data package.
    • The name SHOULD be usable in a url path and SHOULD therefore consist only of alphanumeric characters plus ".", "-" and "_".
    • It would be usual for the name to correspond to the file name (minus the extension) of the data file the resource describes.

Optional Fields

A resource MAY contain any number of additional fields. Common fields include:

  • title: a title or label for the resource.

  • description: a description of the resource.

  • format: 'csv', 'xls', 'json' etc. Would be expected to be the standard file extension for this type of resource.

  • mediatype: the mediatype/mimetype of the resource e.g. 'text/csv', 'application/vnd.ms-excel'

  • encoding: specify the character encoding of the resource's data file. The values should be one of the "Preferred MIME Names" for a character encoding registered with IANA. If no value for this key is specified then the default is UTF-8.

  • bytes: size of the file in bytes

  • hash: the MD5 hash for this resource. Other algorithms can be indicated by prefixing the hash's value with the algorithm name in lower-case. For example:

    "hash": "sha1:8843d7f92416211de9ebb963ff4ce28125932878"

  • schema: a schema or a pointer to the schema for the resource - see below for more on this attribute

  • sources: as for data package metadata.

  • license: as for data package metadata. If not specified the resource inherits from the data package.

Inline Data

Resource data rather than being stored in external files can be shipped 'inline' on a Resource using the data attribute.

The value of the data attribute can be any type of data. However, restrictions of JSON require that the value be a string so for binary data you will need to encode (e.g. to Base64). Information on the type and encoding of the value of the data attribute SHOULD be provided by the format (or mediatype) attribute and the encoding attribute.

Specifically: the value of the data attribute MUST be:

  • EITHER: a JSON array or object - the data is then assumed to be JSON data and SHOULD be processed as such
  • OR: a JSON string - in this case the format or mediatype attributes MUST be provided.

Thus, a consumer of resource object MAY assume if no format or mediatype attribute is provided that the data is JSON and attempt to process it as such.

Examples 1 - inline JSON:

{
   ...
   "resources": [
     {
        "format": "json",
        # some json data e.g. 
        "data": [
           { "a": 1, "b": 2 },
           { .... }
        ]
     }
   ]
}

Example 2 - inline CSV:

{
   ...
   "resources": [
     {
        "format": "csv",
        "data": "A,B,C\n1,2,3\n4,5,6"
     }
   ]
}

Resource Schemas

The value for the schema field on a resource MUST be an Object or a string that "references" an Object as detailed below.

NOTE: the Data Package specification places no restrictions on the form of this Object. This flexibility enables specific communities to define schemas appropriate for the data they manage. As an example, the [Tabular Data Package][tdp] specification requires the schema value to conform to [JSON Table Schema][jts].

#### Schema References

If schema is a string it is a "reference" to an Object and MUST be:

  • EITHER: a URL. The URL MUST:

    • EITHER: resolve to a JSON document that is the schema
    • OR: include a fragment identifier which conforms to to JSON Pointer notation. The URL must then resolve to a JSON document and the schema is obtained by resolving within that JSON document using the fragment identifier as the JSON pointer as per section 6 of the JSON pointer specification. URL.

  • OR: a simple string name which MUST correspond to the 'name' (key) in the schemas object in the same datapackage.json file - see next section.

#### schemas Property

A Data Package MAY have a schemas property. The value of the property MUST be an Object. Each key in the Object is the name of a schema. A schema name MUST consist only of lower-case alphanumeric letters, together with

  • and _.

Each value for an entry in the schemas Object must be an Object specifying an appropriate schema.

Examples

{
  "resources": [
    {
    ...
      "schema": http://url-to/datapackage.json#schemas/schema-name
      }
    }
  ],
...
}

{
  "resources": [
    {
    ...
      "schema": "xyz-schema"
    }
  ],
  "schemas": {
    "xyz-schema": {
      schema goes here ...
    }
  }
}

MediaType

The MediaType [RFC4288] for a Data Package SHOULD be application/vnd.datapackage.

Appendices

Aims

  • Simple
  • Extensible
  • Human editable (for metadata)
  • Machine usable (easily parsable and editable)
  • Based on existing standard formats
  • Not linked to a particular language or system

How It Fits into the Ecosystem

  • Minimal wrapping to provide for machine automated sharing and obtaining of data
  • Data Packages can be registered into and found in indexes (local or remote)
  • Tools (based on code libraries) integrate with these indexes (and storage) to download and upload material

Data Packages and the Wider Ecosystem

Prior Work

The specification is heavily inspired by various software packaging formats. Read the Appendix.