Easy, sharable custom CKAN schemas
by open.canada.ca

ckanext-scheming

This extension provides a way to configure and share CKAN schemas using a JSON schema description. Custom template snippets for editing and display are also supported.

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Requirements

This plugin is compatible with CKAN 2.3 or later.

Configuration

Set the schemas you want to use with configuration options:

ckan.plugins = scheming_datasets

#   module-path:file to schemas being used
scheming.dataset_schemas = ckanext.spatialx:spatialx_schema.json
                           ckanext.spatialx:spatialxy_schema.json
#   will try to load "spatialx_schema.json" and "spatialxy_schema.json"
#   as dataset schemas
#
#   URLs may also be used, e.g:
#
# scheming.dataset_schemas = http://example.com/spatialx_schema.json

#   Preset files may be included as well. The default preset setting is:
scheming.presets = ckanext.scheming:presets.json

#   The is_fallback setting may be changed as well. Defaults to false:
scheming.dataset_fallback = false

Example dataset schemas

These schemas are included in ckanext-scheming and may be enabled with e.g: scheming.dataset_schemas = ckanext.scheming:camel_photos.json

These schemas use presets defined in presets.json.

Schema Keys

scheming_version

Set to 1. Future versions of ckanext-scheming may use a larger number to indicate a change to the description JSON format.

dataset_type

This is the “type” field stored in the dataset. It is also used to set the URL for searching this type of dataset.

Normal datasets would be available under the URL /dataset, but datasets with the camel_photos.json schema above would appear under /camel-photos instead.

about_url

about_url is a Link to human-readable information about this schema. Its use is optional but highly recommended.

dataset_fields, resource_fields

Fields are specified in the order you would like them to appear in the dataset and resource editing pages.

Fields you exclude will not be shown to the end user, and will not be accepted when editing or updating this type of dataset.

Field Keys

field_name

The field_name value is the name of an existing CKAN dataset or resource field or a new new extra field. Existing dataset field names include:

  • name - the URI for the dataset
  • title
  • notes - the dataset description
  • author
  • author_email
  • maintainer
  • maintainer_email

New field names should follow the current lowercase_with_underscores naming convention. Don’t name your field mySpecialField, use my_special_field instead.

This value is available to the form snippet as field.field_name.

label

The label value is a human-readable label for this field as it will appear in the dataset editing form. This label may be a string or an object providing multiple language versions:

{
  "label": {
    "en": "Title",
    "fr": "Titre"
  },
  "...": "..."
}

When using a plain string translations will be provided with gettext:

{
  "label": "Title",
  "...": "..."
}

required

Set to true for fields that must be included. Set to false or don’t include this key for fields that are optional.

Setting to true will mark the field as required in the editing form and include not_empty in the default validators that will be applied when validators is not specified.

To honor this settings with custom validators include scheming_required as the first validator. scheming_required will check the required setting for this field and apply either the not_empty or ignore_missing validator.

choices

The choices list must be provided for select and multiple choice fields. List elements include labels for human-readable text for each element (may be multiple languages like a field label) and values that will be stored in the dataset or resource:

{
  "preset": "select",
  "choices": [
    {
      "value": "bactrian",
      "label": "Bactrian Camel"
    },
    "..."
  ],
  "...": "..."
}

preset

A preset specifies a set of default values for these field keys. They are used to define validation and snippets for common field types.

This extension includes the following presets:

  • "title" - title validation and large text form snippet
  • "select" - validation that choice is from choices, form select box and display snippet
  • "multiple_checkbox" - multiple choice from choices rendered as checkboxes in the form
  • "multiple_select" - multiple choice from choices rendered as a multiple select box in the form
  • "date" - date validation and form snippet
  • "dataset_slug" - dataset slug validation and form snippet that autofills the value from the title field
  • "tag_string_autocomplete" - tag string validation and form autocomplete
  • "dataset_organization" - organization validation and form select box
  • "resource_url_upload" - resource url validaton and link/upload form field
  • "resource_format_autocomplete" - resource format validation with format guessing based on url and autocompleting form field

You may add your own presets by adding them to the scheming.presets configuration setting.

form_snippet

The form_snippet value is the name of the snippet template to use for this field in the dataset or resource editing form. A number of snippets are provided with this extension, but you may also provide your own by creating templates under scheming/form_snippets/ in a template directory in your own extension.

This snippet is passed the field dict containing all the keys and values in this field record, including any additional ones you added to your that aren’t handled by this extension.

This extension includes the following form snippets:

display_snippet

The display_snippet value is the name of the snippet template to use for this field in the dataset, group or organization view page. A number of snippets are provided with this extension, but you may also provide your own by creating templates under scheming/display_snippets/ in a template directory in your own extension.

This snippet is passed the field dict containing all the keys and values in this field record, including any additional ones you added to your that aren’t handled by this extension.

This extension includes the following display snippets:

validators

The validators value is a space-separated string of validator and converter functions to use for this field when creating or updating data. When a validator name is followed by parenthesis the function is called passing the comma-separated values within as string parameters and the result is used as the validator/converter.

e.g. "if_empty_same_as(name) unicode" is the same as in a plugin specifying:

[get_validator('if_empty_same_as')("name"), unicode]

This string does not contain arbitrary python code to be executed, you may only use registered validator functions, optionally calling them with static string values provided.

This extension automatically adds calls to convert_to_extras for new extra fields, so you should not add that to this list.

New validators and converters may be added using the IValidators plugin interface.

Validators that need access to other values in this schema (e.g. to test values against the choices list) may be decorated with the scheming.validation.scheming_validator function. This decorator will make scheming pass this field dict to the validator and use its return value for validation of the field.

CKAN’s validator functions reference lists available validators ready to be used.

output_validators

The output_validators value is like validators but used when retrieving values from the database instead of when saving them. These validators may be used to transform the data before it is sent to the user.

This extension automatically adds calls to convert_from_extras for extra fields so you should not add that to this list.

create_validators

The create_validators value if present overrides validators during create only.

help_text

Only if this key is supplied, its value will be shown as inline help text, Help text must be plain text, no markdown or HTML are allowed. Help text may be provided in multiple languages like label fields.

help_inline

Display help text inline if set to true. Default is false.

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