The CKAN API version 1 & 2 is separated into three parts.
The resources, methods, and data formats of each are described below.
These are very similar, but when the API returns a reference to an object, Version 1 API will return the Name of the object (e.g. "river-pollution") and Version 2 API will return the ID of the object (e.g. "a3dd8f64-9078-4f04-845c-e3f047125028").
The reason for this is that Names can change, so to reliably refer to the same dataset every time, you will want to use the ID and therefore use API v2. Alternatively, many people prefer to deal with Names, so API v1 suits them.
When making requests, you can call objects by either their Name or ID, interchangeably.
The only exception for this is for Tag objects. Since Tag names are immutable, they are always referred to with their Name.
The locator for a given resource can be formed by appending the relative path for that resource to the API locator.
Resource Locator = API Locator + Resource Path
The API locators for the CKAN APIs (by version) are:
/api
(version 1)/api/1
(version 1)/api/2
(version 2)
The relative paths for each resource are listed in the sections below.
Model resources are available at published locations. They are represented with a variety of data formats. Each resource location supports a number of methods.
The data formats of the requests and the responses are defined below.
Here are the resources of the Model API.
Model Resource | Location |
---|---|
Dataset Register | /rest/dataset |
Dataset Entity | /rest/dataset/DATASET-REF |
Group Register | /rest/group |
Group Entity | /rest/group/GROUP-REF |
Tag Register | /rest/tag |
Tag Entity | /rest/tag/TAG-NAME |
Rating Register | /rest/rating |
Dataset Relationships Register | /rest/dataset/DATASET-REF/relationships |
Dataset Relationships Register | /rest/dataset/DATASET-REF/RELATIONSHIP-TYPE |
Dataset Relationships Register | /rest/dataset/DATASET-REF/relationships/DATASET-REF |
Dataset Relationship Entity | /rest/dataset/DATASET-REF/RELATIONSHIP-TYPE/DATASET-REF |
Dataset's Revisions Entity | /rest/dataset/DATASET-REF/revisions |
Revision Register | /rest/revision |
Revision Entity | /rest/revision/REVISION-ID |
License List | /rest/licenses |
Possible values for DATASET-REF are the dataset id, or the current dataset name.
Possible values for RELATIONSHIP-TYPE are described in the Relationship-Type data format.
Here are the methods of the Model API.
Resource | Method | Request | Response |
---|---|---|---|
Dataset Register | GET | Dataset-List | |
Dataset Register | POST | Dataset | |
Dataset Entity | GET | Dataset | |
Dataset Entity | PUT | Dataset | |
Group Register | GET | Group-List | |
Group Register | POST | Group | |
Group Entity | GET | Group | |
Group Entity | PUT | Group | |
Tag Register | GET | Tag-List | |
Tag Entity | GET | Dataset-List | |
Rating Register | POST | Rating | |
Rating Entity | GET | Rating | |
Dataset Relationships Register | GET | Pkg-Relationships | |
Dataset Relationship Entity | GET | Pkg-Relationship | |
Dataset Relationships Register | POST | Pkg-Relationship | |
Dataset Relationship Entity | PUT | Pkg-Relationship | |
Dataset's Revisions Entity | GET | Pkg-Revisions | |
Revision List | GET | Revision-List | |
Revision Entity | GET | Revision | |
License List | GET | License-List |
In general:
- GET to a register resource will list the entities of that type.
- GET of an entity resource will show the entity's properties.
- POST of entity data to a register resource will create the new entity.
- PUT of entity data to an existing entity resource will update it.
It is usually clear whether you are trying to create or update, so in these cases, HTTP POST and PUT methods are accepted by CKAN interchangeably.
Here are the data formats for the Model API:
Name | Format |
---|---|
Dataset-Ref | Dataset-Name-String (API v1) OR Dataset-Id-Uuid (API v2) |
Dataset-List | [ Dataset-Ref, Dataset-Ref, Dataset-Ref, ... ] |
Dataset | { id: Uuid, name: Name-String, title: String, version: String, url: String, resources: [ Resource, Resource, ...], author: String, author_email: String, maintainer: String, maintainer_email: String, license_id: String, tags: Tag-List, notes: String, extras: { Name-String: String, ... } } See note below on additional fields upon GET of a dataset. |
Group-Ref | Group-Name-String (API v1) OR Group-Id-Uuid (API v2) |
Group-List | [ Group-Ref, Group-Ref, Group-Ref, ... ] |
Group | { name: Group-Name-String, title: String, description: String, packages: Dataset-List } |
Tag-List | [ Name-String, Name-String, Name-String, ... ] |
Tag | { name: Name-String } |
Resource | { url: String, format: String, description: String, hash: String } |
Rating | { dataset: Name-String, rating: int } |
Pkg-Relationships | [ Pkg-Relationship, Pkg-Relationship, ... ] |
Pkg-Relationship | { subject: Dataset-Name-String, object: Dataset-Name-String, type: Relationship-Type, comment: String } |
Pkg-Revisions | [ Pkg-Revision, Pkg-Revision, Pkg-Revision, ... ] |
Pkg-Revision | { id: Uuid, message: String, author: String, timestamp: Date-Time } |
Relationship-Type | One of: 'depends_on', 'dependency_of', 'derives_from', 'has_derivation', 'child_of', 'parent_of', 'links_to', 'linked_from'. |
Revision-List | [ revision_id, revision_id, revision_id, ... ] |
Revision | { id: Uuid, message: String, author: String, timestamp: Date-Time, datasets: Dataset-List } |
License-List | [ License, License, License, ... ] |
License | { id: Name-String, title: String, is_okd_compliant: Boolean, is_osi_compliant: Boolean, tags: Tag-List, family: String, url: String, maintainer: String, date_created: Date-Time, status: String } |
To send request data, create the JSON-format string (encode in UTF8) put it in the request body and send it using PUT or POST.
Response data will be in the response body in JSON format.
Notes:
- When you update an object, fields that you don't supply will remain as they were before.
- To delete an 'extra' key-value pair, supply the key with JSON value:
null
- When you read a dataset, some additional information is supplied that you cannot modify and POST back to the CKAN API. These 'read-only' fields are provided only on the Dataset GET. This is a convenience to clients, to save further requests. This applies to the following fields:
Key | Description |
---|---|
id | Unique Uuid for the Dataset |
revision_id | Latest revision ID for the core Package data (but is not affected by changes to tags, groups, extras, relationships etc) |
metadata_created | Date the Dataset (record) was created |
metadata_modified | Date the Dataset (record) was last modified |
relationships ratings_average ratings_count |
info on Dataset Relationships |
ckan_url | full URL of the Dataset |
download_url (API v1) | URL of the first Resource |
isopen | boolean indication of whether dataset is open according to Open Knowledge Definition, based on other fields |
notes_rendered | HTML rendered version of the Notes field (which may contain Markdown) |
Search resources are available at published locations. They are represented with a variety of data formats. Each resource location supports a number of methods.
The data formats of the requests and the responses are defined below.
Here are the published resources of the Search API.
Search Resource | Location |
---|---|
Dataset Search | /search/dataset |
Resource Search | /search/resource |
Revision Search | /search/revision |
Tag Counts | /tag_counts |
See below for more information about dataset and revision search parameters.
Here are the methods of the Search API.
Resource | Method | Request | Response |
---|---|---|---|
Dataset Search | POST | Dataset-Search-Params | Dataset-Search-Response |
Resource Search | POST | Resource-Search-Params | Resource-Search-Response |
Revision Search | POST | Revision-Search-Params | Revision-List |
Tag Counts | GET | Tag-Count-List |
It is also possible to supply the search parameters in the URL of a GET request, for example /api/search/dataset?q=geodata&allfields=1
.
Here are the data formats for the Search API.
Name | Format |
---|---|
Dataset-Search-Params Resource-Search-Params Revision-Search-Params | { Param-Key: Param-Value, Param-Key: Param-Value, ... } See below for full details of search parameters across the various domain objects. |
Dataset-Search-Response | { count: Count-int, results: [Dataset, Dataset, ... ] } |
Resource-Search-Response | { count: Count-int, results: [Resource, Resource, ... ] } |
Revision-List | [ Revision-Id, Revision-Id, Revision-Id, ... ] NB: Ordered with youngest revision first |
Tag-Count-List | [ [Name-String, Integer], [Name-String, Integer], ... ] |
The Dataset
and Revision
data formats are as defined in Model Formats.
Dataset Parameters
Param-Key | Param-Value | Examples | Notes |
---|---|---|---|
q | Search-String | q=geodata q=government+sweden q=%22drug%20abuse%22 q=tags:"river pollution" |
Criteria to search the dataset fields for. URL-encoded search text. (You can also concatenate words with a '+' symbol in a URL.) Search results must contain all the specified words. You can also search within specific fields. |
qjson | JSON encoded options | ['q':'geodata'] | All search parameters can be json-encoded and supplied to this parameter as a more flexible alternative in GET requests. |
title, tags, notes, groups, author, maintainer, update_frequency, or any 'extra' field name e.g. department | Search-String | title=uk&tags=health department=environment tags=health&tags=pollution tags=river%20pollution |
Search in a particular a field. |
order_by | field-name (default=rank) | order_by=name | Specify either rank or the field to sort the results by |
offset, limit | result-int (defaults: offset=0, limit=20) | offset=40&limit=20 | Pagination options. Offset is the number of the first result and limit is the number of results to return. |
all_fields | 0 (default) or 1 | all_fields=1 | Each matching search result is given as either a dataset name (0) or the full dataset record (1). |
Note
filter_by_openness and filter_by_downloadable were dropped from CKAN version 1.5 onwards.
Resource Parameters
Param-Key | Param-Value | Example | Notes |
---|---|---|---|
url, format, description | Search-String | url=statistics.org format=xls description=Research+Institute |
Criteria to search the dataset fields for. URL-encoded search text. This search string must be found somewhere within the field to match. Case insensitive. |
qjson | JSON encoded options | ['url':'www.statistics.org'] | All search parameters can be json-encoded and supplied to this parameter as a more flexible alternative in GET requests. |
hash | Search-String | hash=b0d7c260-35d4-42ab-9e3d-c1f4db9bc2f0 | Searches for an match of the hash field. An exact match or match up to the length of the hash given. |
all_fields | 0 (default) or 1 | all_fields=1 | Each matching search result is given as either an ID (0) or the full resource record |
offset, limit | result-int (defaults: offset=0, limit=20) | offset=40&limit=20 | Pagination options. Offset is the number of the first result and limit is the number of results to return. |
Note
Powerful searching from the command-line can be achieved with curl and the qjson parameter. In this case you need to remember to escapt the curly braces and use url encoding (e.g. spaces become %20
). For example:
curl 'http://thedatahub.org/api/search/dataset?qjson=\{"author":"The%20Stationery%20Office%20Limited"\}'
Revision Parameters
Param-Key | Param-Value | Example | Notes |
---|---|---|---|
since_time | Date-Time | since_time=2010-05-05T19:42:45.854533 | The time can be less precisely stated (e.g 2010-05-05). |
since_id | Uuid | since_id=6c9f32ef-1f93-4b2f-891b-fd01924ebe08 | The stated id will not be included in the results. |
Standard HTTP status codes are used to signal method outcomes.
Code | Name |
---|---|
200 | OK |
201 | OK and new object created (referred to in the Location header) |
301 | Moved Permanently |
400 | Bad Request |
403 | Not Authorized |
404 | Not Found |
409 | Conflict (e.g. name already exists) |
500 | Service Error |