ckanext-scheming

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

Requirements

This plugin is compatible with CKAN 2.6 or later.

Installation

You can install the extension with the following shell commands:

cd $CKAN_VENV/src/

pip install -e "git+https://github.com/ckan/ckanext-scheming.git#egg=ckanext-scheming"
pip install -r ckanext-scheming/requirements.txt

Configuration

Set the schemas you want to use with configuration options:

# Each of the plugins is optional depending on your use
ckan.plugins = scheming_datasets scheming_groups scheming_organizations

#   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

#   For group and organization schemas (replace myplugin with your custom plugin)
scheming.group_schemas = ckanext.scheming:group_with_bookface.json
                         ckanext.myplugin:/etc/ckan/default/group_with_custom_fields.json
scheming.organization_schemas = ckanext.scheming:org_with_dept_id.json
                                ckanext.myplugin:org_with_custom_fields.json
#
#   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

Different Types of Schemas

With this plugin, you can customize the group, organization, and dataset entities in CKAN. Adding and enabling a schema will modify the forms used to update and create each entity, indicated by the respective type property at the root level. Such as group_type, organization_type, and dataset_type. Non-default types are supported properly in CKAN 2.8+ only as is indicated throughout the examples.

Creating custom group or organization types is only supported in CKAN 2.8, instructions for that are below

---

Top-level Schema Keys (Common among dataset, group, and organization schemas)

scheming_version

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

about_url

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

---

Example Schemas - Datasets

• default dataset schema
• camel photos schema

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 - Datasets

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.

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.

---

Example Schemas - Group

• Default group schema with field modifications
• Group with custom type (CKAN 2.8+ only)

Example Schemas - Organization

• Default organization schema with field modifications
• Organization with custom type (CKAN 2.8+ only)

Schema Keys - Groups / Organization

group_type

Examples:

• "group_type": "group" used for modifying the default group schema
• "group_type": "theme" an example of defining a custom group type, as seen in the above examples (CKAN 2.8+ only)

organization_type

Examples:

• "organization_type": "organization" used for modifying the default organization schema
• "organization_type": "publisher" an example of defining a custom organization type, as seen in the above examples (CKAN 2.8+ only)

fields

The dataset_fields and resource_fields schema properties don't exist in group or organization schemas. Instead, they just have a fields property.

URLs

Like dataset_type, a group_type of group allows you to customize the default group schema under the URL /group, such as the modified schema in group_with_bookface.json, but a schema with a custom type (CKAN 2.8+ only) such as custom_group_with_status.json schema above would appear under /theme instead, because its group_type field is set to "theme".

---

Field Keys

field_name

The field_name value is the name of an existing CKAN dataset or resource field or a 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 may 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"
    },
    "..."
  ],
  "...": "..."
}

choices_helper

If a choices list is not provided you must provide a choices_helper function that will return a list of choices in the same format as the choices list above.

You may register your own helper function or use the scheming_datastore_choices helper included in ckanext-scheming:

{
  "preset": "select",
  "choices_helper": "scheming_datastore_choices",
  "datastore_choices_resource": "countries-resource-id-or-alias",
  "datastore_choices_columns": {
    "value": "Country Code",
    "label": "English Country Name"
  }
}

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
• "datetime" date and time 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
  • "organization_url_upload" - organization url validaton and link/upload form field
• "resource_format_autocomplete" - resource format validation with format guessing based on url and autocompleting form field
• "json_object" - JSON based input. Only JSON objects are supported. The input JSON will be loaded during output (eg when loading the dataset in a template or via the API).

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:

• text.html - a simple text field for free-form text or numbers (default)
• large_text.html - a larger text field, typically used for the title
• date.html - a date widget with an html5 date picker
• slug.html - the default name (URL) field
• license.html - a dataset license selection field
• markdown.html - a markdown field, often used for descriptions
• organization.html - an organization selection field for datasets
• upload.html - an upload field for resource files
  • organization_upload.html - an upload field for organization logo files
• select.html - a select box
• multiple_checkbox.html - a group of checkboxes
• multiple_select.html - a multiple select box

display_snippet

The display_snippet value is the name of the snippet template to use for this field in the dataset, resource, 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:

• text.html - render as a normal text value (default)
• link.html - render as an external link to open in a new window
• email.html - render as a "mailto:" link
• select.html - show the label text for the choice selected
• multiple_choice.html - show the label text for all choices selected

If null is passed as value in display_snippet, it will remove the field from being displayed at the view page.

select_size

Set to the number of choices to display in select, multiple_select and multiple_check_box form and display snippets.

sorted_choices

Set to "true" to sort choices alphabetically in form and 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.

Running the Tests

To run the tests:

pytest --ckan-ini=test.ini ckanext/scheming/tests