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.

Table of contents:

1. Requirements
2. Installation
3. Configuration
   • Schema Types
   • Example Schemas
   • Storing non-string data
   • Common Schema Keys
     • scheming_version
     • about_url
   • Dataset Schema Keys
     • dataset_type
     • dataset_fields, resource_fields
     • before_validators, after_validators
   • Group / Organization Schema Keys
     • group_type
     • organization_type
     • fields
     • before_validators, after_validators
   • Field Keys
     • field_name
     • label
     • repeating_subfields
     • start_form_page
     • required
     • choices
     • choices_helper
     • default
     • default_jinja2
     • preset
     • form_snippet
     • display_snippet
     • display_property
     • validators
     • output_validators
     • create_validators
     • help_text
4. Action API Endpoints
5. Running the Tests

Requirements

This plugin is compatible with CKAN 2.9 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 as is indicated throughout the examples.

Example Schemas

Dataset schemas:

• default dataset schema
• camel photos schema
• subfields schema
• form pages schema

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:

• Default group schema with field modifications
• Group with custom type

Organization schemas:

• Default organization schema with field modifications
• Organization with custom type

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.

before_validators, after_validators

before_validators: validator_name

after_validators: validator_name

Runs validator functions before and after the dataset_type package is created/updated.

Group / Organization Schema Keys

group_type

group_type: group

is used for modifying the default group schema

group_type: theme

is an example of defining a custom group type, as seen in the example schemas above

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 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

organization_type: organization

is used for modifying the default organization schema

organization_type: publisher

is an example of defining a custom organization type, as seen in the example schemas above

fields

fields:

- field_name: title
  label: Name
  form_snippet: large_text.html
  form_attrs:
    data_module: slug-preview-target
  form_placeholder: My Organization

...

A single fields list replaces the dataset_fields and resource_fields schema properties doin dataset schemas.

before_validators, after_validators

before_validators: validator_name

after_validators: validator_name

Runs validator functions before and after the organization_type/group_type group is created/updated.

---

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.

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:

- field_name: title
  label:
    en: Title
    fr: Titre

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

- field_name: title
  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.

NOTE: 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+ only. Form pages for dataset type only supported by CKAN 2.10+ or with ckan/ckan#7032 . Adding start_form_page 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

  field_name: address
  label: Address

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

  required: true

Use 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.

NOTE: 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:

- field_name: category
  preset: select
  choices:
  - value: bactrian
    label: Bactrian Camel
  - value: hybrid
    label: Hybrid Camel

For storing non-string values see output_validators.

For required select fields you may also want to add this setting so that users are forced to choose an item in the form, otherwise the first choice will be selected in the form by default:

  form_include_blank_choice: true

To set the number of choices displayed in the multiple_select form snippets use:

  select_size: 5

To sort choices alphabetically in form and display snippets use:

  sorted_choices: true

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:

- field_name: country
  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

default

Pre-fill new forms with this default value for this field.

default_jinja2

Pre-fill new forms with a jinja2 snippet defined by default_jinja2, useful if you need to call a template helper function or use jinja2 logic to determine the default value for this field.

preset

A preset specifies a set of default values for other field keys. They allow reuse of definitions for validation and snippets for common field types.

This extension includes the following presets in presets.json:

  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 and form autocomplete

  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 define your own presets by adding additional files 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.

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 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]

If parameters can be parsed as a valid python literals, they are passed with original type. If not, all parameters passed as strings. In addition, space character is not allowed in argument position. Use its HEX code instead \\x20.

  validators: xxx(hello,world)    # xxx("hello", "world")
  validators: xxx(hello,1)        # xxx("hello", "1")
  validators: xxx("hello",1,None) # xxx("hello", 1, None)
  validators: xxx("hello\\x20world") # xxx("hello world")

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.

NOTE: ckanext-scheming automatically adds calls to convert_to_extras for extra fields when required.

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

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: scheming_required boolean_validator
    output_validators: boolean_validator

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.

NOTE: ckanext-scheming automatically adds calls to convert_from_extras for extra fields when required.

create_validators

The create_validators value if present overrides validators during create only.

help_text

  help_text: License definitions and additional information

If this key is supplied, its value will be shown after the field as help text. Help text may be provided in multiple languages like label fields.

Help text must be plain text, no markdown or HTML are allowed unless:

  help_allow_html: true

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

Adjust the position of help_text with:

  help_inline: true

Display help text inline (next to the field) if set to true. Default is false (display help text under the field).

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