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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.

Tests

Table of contents:

  1. Requirements
  2. Installation
  3. Configuration
  4. Action API Endpoints
  5. Running the Tests

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"

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.yaml
                           ckanext.spatialx:spatialxy_schema.yaml
#   will try to load "spatialx_schema.yaml" and "spatialxy_schema.yaml"
#   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.yaml

#   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

Schema Types

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

Example Schemas

Dataset schemas:

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

These schemas use presets defined in presets.json.

Group schemas:

Organization schemas:

Storing non-string data

Internally all extra fields are stored as strings. If you are attempting to save and restore other types of data you will need to use output validators.

For example if you use a simple "yes/no" question, you will need to let ckanext-scheming know that this data needs to be stored and retrieved as a boolean. This is acheieved using validators and output_validators keys.

  - field_name: is_camel_friendly
    label: Is this camel friendly?
    required: true
    preset: select
    choices:
      - value: false
        label: "No"
      - value: true
        label: "Yes"
    validators: boolean_validator
    output_validators: boolean_validator

output_validators are run to convert the internal string representation of a field to something else. This means it is used to return things like lists of strings or nested objects.

Common Schema Keys

scheming_version

Set to 2. Future versions of ckanext-scheming may use a larger number to indicate a change to the schema format.

about_url

about_url: https://github.com/link-to-my-project

about_url is a link to human-readable information about this schema. ckanext-scheming automatically publishes your schema and this link allows users to learn more about it.

Dataset Schema Keys

dataset_type

dataset_type: camel-photos

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

dataset_fields:

- field_name: title
  label: Title
  preset: title

- field_name: name
  label: URL
  preset: dataset_slug

...

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.

Group / Organization Schema Keys

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)

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".

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.

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

repeating_subfields

This field is the parent of group of repeating subfields. The value is a list of fields entered the same way as normal fields. CKAN 2.8+ only

CKAN needs an IPackageController plugin with before_index to convert repeating subfields to formats that can be indexed by solr. For testing you may use the included scheming_nerf_index plugin to encode all repeating fields as JSON strings to prevent solr errors.

repeating_label may be used to provide a singular version of the label for each group.

field_name: contacts
label: Contacts
repeating_label: Contact
repeating_subfields:
  - field_name: address
    label: Address
    required: true

  - field_name: city
    label: City

  - field_name: phone
    label: Phone Number

start_form_page

Dataset fields may be divided into separate form pages for creation and editing. CKAN 2.9+ feature only. Form pages for dataset type only supported by CKAN 2.10+ or with ckan/ckan#7032 . Adding this key to a field marks this field as the start of a new page of fields.

- start_form_page:
    title: Detailed Metadata
    description:
      These fields improve search and give users important links

A title and description should be provided to help with navigation. These values may be strings or objects providing multiple language versions of text.

required

Use required: 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
- value: hybrid
  label: Hybrid Camel

For required select fields you may also want to add

form_include_blank_choice: true

so that users are forced to choose an item in the form, otherwise the first choice will be selected in the form by default.

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
datastore_additional_choices:
- value: none
  label: None
- value: na
  label: N/A

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:

  • preset: title - title validation and large text form snippet
  • preset: select - validation that choice is from choices, form select box and display snippet
  • preset: radio - validation that choice is from choices, form radio buttons group and display snippet
  • preset: multiple_checkbox - multiple choice from choices rendered as checkboxes in the form, stored as a list of values
  • preset: multiple_select - multiple choice from choices rendered as a multiple select box in the form, stored as a list of values
  • preset: multiple_text - repeating text field with add and remove buttons, stored as a list of strings
  • preset: date - date validation and form snippet
  • preset: datetime date and time validation and form snippet
  • preset: dataset_slug - dataset slug validation and form snippet that autofills the value from the title field
  • preset: tag_string_autocomplete - tag string validation and form autocomplete
  • preset: dataset_organization - organization validation and form select box
  • preset: resource_url_upload - resource url validaton and link/upload form field
  • preset: resource_format_autocomplete - resource format validation with
  • preset: organization_url_upload - organization url validaton and link/upload form field format guessing based on url and autocompleting form field
  • preset: 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).
  • preset: markdown - markdown text area and display

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.

The included form snippets may be found under templates/scheming/form_snippets.

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.

The included display snippets may be found under templates/scheming/display_snippets.

If display_snippet: null is used the field will be removed from the view page.

display_property

- field_name: author
  label: Author
  display_property: dc:creator

Set a property attribute on dataset fields displayed as "Additional Info", useful for adding RDF markup.

select_size

select_size: 5

Set to the number of choices to display in the multiple_select form 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.

validators: if_empty_same_as(name) unicode_safe

is the same as a plugin using the validators:

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

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_allow_html

Allow HTML inside the help text if set to true. Default is false.

help_inline

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

Action API Endpoints

The extension adds action endpoints which expose any configured schemas via: https://github.com/ckan/ckanext-scheming/blob/master/ckanext/scheming/logic.py

Some examples:

Calling http://localhost:5000/api/3/action/scheming_dataset_schema_list

Returns:

{
  help: "http://localhost:5005/api/3/action/help_show?name=scheming_dataset_schema_list",
  success: true,
  result: [
    "dataset",
    "camel-photos"
  ]
}

Calling http://localhost:5000/api/3/action/scheming_dataset_schema_show?type=dataset

Returns:

{
  help: "http://localhost:5005/api/3/action/help_show?name=scheming_dataset_schema_show",
  success: true,
  result: {
    scheming_version: 2,
    dataset_type: "dataset",
    about: "A reimplementation of the default CKAN dataset schema",
    about_url: "http://github.com/ckan/ckanext-scheming",
    dataset_fields: [...],
    resource_fields: [...]
  }
}

The full list of API actions are available in ckanext/scheming/logic.py

Running the Tests

To run the tests:

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