Introduction

The Data Repository REST API can be used for interaction with the service via external services or applications, for example for integration with other websites (research community portals) or for uploading or downloading large data sets that are not easily handled via a web browser.

This page explains the basic concepts, authentication and all existing HTTP requests that can currently be used. In the next pages, the examples given are done using cURL commands. This tool can be freely downloaded for any OS.

Basic concepts

The Data Repository service uses several concepts which are briefly explained below.

A scientific community has the roles of creating and maintaining metadata schemas and curating the datasets which are part of a scientific domain or research project. Users of the Data Repository can be part of one or more communities. Some selected members of a community are also given the role of community administrators, which grants them the special rights needed for the schema definitions and deposit curation tasks.

Any registered user can upload scientific datasets into Data Repository and thus create data deposits. A deposit is comprised of data files and associated metadata. The deposit’s metadata consists of a set of common fixed metadata fields and a set of custom metadata blocks, each block containing related metadata fields. A deposit is always connected to one scientific community which has the role of curating and maintaining it (except for deposits created as part of the generic SURF community).

A deposit contains a set of common metadata fields and a set of custom metadata blocks. This metadata is not free form, however, but is governed by static schemas; the common metadata schema is set by Data Repository and defines a superset of Dublin Core elements, while the schema for the custom metadata block is specific to each community and can be customized by the community administrators. In order to be accepted, the deposits submitted to a community must conform to the schema required by the community.

Object state

An object (such as a deposit or collection) can exist in several states. Immediately after creation a deposit enters the ‘draft’ state. In this state the deposit is only accessible by its owner and can be freely modified: its metadata can be changed and files can be uploaded into or removed from it. A draft can be published at any time, and through this action it changes its state from ‘draft’ to ‘published’, is assigned persistent identifiers, and becomes publicly accessible. Please note that after publication, the list of files in a published deposit cannot be changed.

To update the metadata of a deposit through the API, a JSON Patch must be supplied with the request. Please read the documentation on this website carefully to fully understand how these patches work.

Making requests

The REST API is used by making API requests using the methods of the standard HTTP protocol. Typically an application like cURL is used to make requests, but it is also possible to do this from within your tools or custom-built applications.

If a request is received by the Data Repository, it will be processed and a response will be given. This response is according to the HTTP protocol and will include a status code indicating whether the processing of the request was successful or an error occured. Based on this code a body is included that either gives the updated state of the object being requested or modified, or a description of the error that occurred. The response data will almost always be in JSON format, except when for example images, files or XML data is requested.

Of all requests being made, the data must be provided in JSON or JSON Patch format. To indicate what kind of data is provided, a request header entry must be added, namely the Content-type header valued application/json;charset=UTF-8 or application/json-patch+json;charset=UTF-8 respectively. This generally only applies to requests that use the POST or PATCH method.

By making a set of requests successively, an existing object can be modified in its description, relationship to other objects or visibility on the web interface. More importantly, new objects can be created from scratch that contain descriptive metadata and files for publication.

Object identifiers

Every object stored in the Data Repository has a unique identifier. To access a specific object using the REST API, this object identifier needs to be provided as part of the URL. These identifiers always consists of a namespace followed by a colon : and the object identifier itself. For example, a deposit usually looks like deposit:c800a32839fa47d9, where the namespace here is deposit. For large datasets it is possible that the namespace for deposits differ, e.g. cosmogrid:128 is then also possible.

For collections, the namespace is always collection. For an overview of all namespaces and example object identifiers, see the table below:

Type Namespace Example identifiers
Deposit deposit or anything not listed here deposit:c800a32839fa47d9 or cosmogrid:471
Collection collection collection:cosmogrid
Community community community:surf
Group group group:80a32839fa47d9aa
Schema schema schema:dublin

For objects created using the REST API, the default namespace for any object type is used.

Responses

All request responses will be in JSON format and UTF-8 encoded, indicated by the Content-type header valued application/json;charset=UTF-8.

A deposit is represented as a typical JSON object with keys and their values:

{
  "field1": "value"
}

A collection of deposits is represented as a JSON array of objects:

{
  "collection": [
    {
      "field1": "value",
      "field2": "value"
    },
    {
      "field1": "value",
      "field2": "value"
    }
  ]
}

Timestamps are in UTC and formatted according to ISO 8601:

{
  "updated": "YYYY-MM-DDTHH:MM:SS.ssssssZ"
}

In case a request fails, the body of the response body contains details about the error, for Command:

{
  "message": "The requested URL was not found on the server.  If you entered the URL manually please check your spelling and try again.",
  "code": 404
}

Herein the message field provides a detailed description of what went wrong, while the code indicates the HTTP status code (equivalent to the request response status code).

Status codes

The request status codes indicate whether the request was successfully received, processed and/or executed. The Data Repository service follows the globally accepted list of HTTP status codes in all cases.

One of the following status codes is returned in case the request was successful:

200 - Request was successfully received and executed, see body for results

201 - Object created, see body for results

204 - No contents, this occurs when for example an object is successfully deleted

In case the request failed, the body of the response usually contains details, and one of the following status codes is returned:

400 - Request was not understood

401 - User must authenticate first, usually because no access token was provided with the request

403 - User is not authorized to perform request, missing permission to do so

404 - Requested object not found or API endpoint does not exist

Any status code greater then or equal to 500 indicates that internally something went wrong in the server. If in this case the problem persists, kindly report this to SURF.

Authentication

Although listing and accessing public data is not access-controlled, only registered users can use the API to its full extent. Authentication during requests is done by passing an access token along with the request. The access token is an randomly-generated string which can be created in the Data Repository user account page after logging in to the web user interface. See API tokens.

Hosts

Unless you are using an instance of Data Repository hosted by yourself or your institution, different hosts are available for different purposes. Make sure to select the host that suits your needs. For every host specific authorization is needed and to log in you need to register with SURF first.

Host Address Use when
Test https://tdr-test.surfsara.nl You are actively participating in a pilot or test project with SURF.
Training https://trng-repository.surfsara.nl You want to make a test upload or are participating in a training.
Production https://repository.surfsara.nl You want to make an actual data publication.

In the documentation from now on the selected host will be shown as a variable $SDR_HOST. Keep in mind that for different hosts you need different API access tokens, so make sure to generate one in the currently-used host.

General usage

The general command to use the REST API looks as follows (using cURL):

curl https://$SDR_HOST/api/$PATH

where SDR_HOST is the Data Repository host you want to communicate with (typically repository.surfsara.nl) and PATH is the endpoint to use. An endpoint uniquely identifies the resource(s) you are requesting or want to modify. See below for more information.

To authenticate yourself during a request, use the token parameter (see API tokens to generate a token):

curl https://$SDR_HOST/api/$PATH?token=$TOKEN

Depending on the result you want to achieve and the request you want to make, you can change the method for the request (default GET), e.g. to post a change to specific deposit (see also next section):

curl -X POST https://$SDR_HOST/api/objects/deposit/1?token=$TOKEN

Methods

In the table below, the most used HTTP methods for interaction using the REST API are listed.

Method Authentication required Typical use
GET Typically no Get current state of an object or resource, including header information
POST Yes Create new object
PUT Yes Upload file to deposit
PATCH Yes Update descriptive metadata state of an object or resource
DELETE Yes Delete a (part of a) resource or object
HEAD Typically no Identical to GET method, but without response body

Endpoints

An endpoint uniquely identifies the resource(s) you are requesting or want to modify. An endpoint always starts with the general /api part and is logically followed by the type of information represented in the endpoint. Optionally a unique identifier that represents a resource or object can be added.

In the table below, some endpoints are listed together with the available methods:

Endpoint Methods Description
/api GET General information about the REST API
/api/objects GET Object listing and search (with parameters)
/api/objects/deposit/<id> GET, POST, PATCH Deposit object metadata retrieval or updates
/api/objects/collection/<id> GET, POST, PATCH Collection object metadata retrieval or updates
/api/objects/community/<id> GET Community object metadata retrieval
/api/objects/group/<id> GET Group object metadata retrieval
/api/objects/schema/<id> GET Schema object metadata retrieval

Objects

In the table below, the available object types and corresponding operations for interaction using the REST API are listed.

Type Operations
Deposit List, retrieve, create, modify, publish, delete (draft)
Collection List, retrieve, create, modify, publish, delete (draft)
Community List, retrieve
Group List, retrieve
Schema List, retrieve

Integration

The Data Repository REST API can be integrated in any workflow or application as long as they adhere to the required workflows.

Integration with Python

To intergrate the API in your application using Python, please make use of the ‘requests’ package that allows excellent and straightforward interaction possibilities from within your Python scripts.