FAIR signposting middleware for Django

django_signposting is a Django middleware library that facilitates the addition of FAIR signposting headers to HTTP responses. This middleware helps in making your data more FAIR (Findable, accessible, interoperable, reuseable) by embedding signposting headers in responses, guiding clients to relevant resources linked to the response content.

Based on the Signposting library.

Features

Automatically adds signposting headers to HTTP responses.
Signposts can be added manually or automatically be parsed from JSON-LD/schema.org
Supports multiple relation types with optional media type specification.
Easily integrable with existing Django applications.

Signposts are formatted and added as Link headers

curl -I http://localhost:8000
HTTP/2 200 
...
link: <https://schema.org/Dataset> ; rel="type" ,
      <https://orcid.org/0000-0001-9447-460X> ; rel="author" ,
      <https://example.com/download.zip> ; rel="item" ; type="application/zip"

Installation

pip install django-signposting

Usage

Automatic parsing of JSON-LD

The library can automatically add signposts to web pages that already make metadata available via JSON-LD in HTML via <script type="application/ld+json"> tags, i.e.:

<!DOCTYPE html>
<html>
<head>

<script type="application/ld+json">{"@context": "https://schema.org", "@type": ["WebSite", "Dataset"], "author": {"@type": "Person", "name": "Daniel Bauer", "url": "https://orcid.org/0000-0001-9447-460X"}, "description": "A dataset of things.", "hasPart": [{"@type": "ImageObject", "encodingFormat": "image/png", "url": "http://example.com/image.png"}, {"@type": "ImageObject", "encodingFormat": "image/png", "url": "http://example.com/image2.png"}], "license": {"@type": "CreativeWork", "name": "CC BY 4.0", "url": "https://creativecommons.org/licenses/by/4.0/"}, "name": "My Dataset", "sameAs": [{"@type": "MediaObject", "contentUrl": "https://example.com/download.zip", "encodingFormat": "application/zip"}, {"@type": "MediaObject", "contentUrl": "https://example.com/metadata.json"}], "url": "https://example.com"}</script>
</head>
<body>
    <p>Hello, world!</p>
</body>
</html>

To enable automatic parsing of JSON-LD, add the following middleware classes to your Django project's MIDDLEWARE setting in settings.py:

MIDDLEWARE = [
    ...,
    'django_signposting.middleware.SignpostingMiddleware',
    'django_signposting.middleware.JsonLdSignpostingParserMiddleware',
    ...,
]

This extracts supported metadatad properties from JSON-LD and adds the corresponding signposting headers to the HttpResponse automatically.

Automatic parsing is compatible with extensions that provide JSON-LD as part of a web page, such as django-json-ld. It can also extract signposts from rich metadata descriptions of datasets such as detached RO-Crates (see example views).

Note: The middleware order is important! Place SignpostingMiddleware before JsonLdSignpostingParserMiddleware to ensure proper extraction and processing of JSON-LD content.

Alternative approaches

Manual signposting

For cases where there is no embedded JSON-LD, or you want to specify additional headers manually, you can use the add_signposts utility function. This still requires the SignpostingMiddleware to inject the links into the response:

Add Middleware: Add the SignpostingMiddleware to your Django project's MIDDLEWARE setting in settings.py:

MIDDLEWARE = [
    ...,
    'django_signposting.middleware.SignpostingMiddleware',
    ...,
]

Add Signposts to your Views: Use the add_signposts utility function:

from django.http import HttpResponse
from django_signposting.utils import add_signposts
from signposting import Signpost, LinkRel

def my_view(request):
    response = HttpResponse("Hello, world!")
    
    # Add signpostings as string
    add_signposts(
        response,
        Signpost(LinkRel.type, "https://schema.org/Dataset"),
        Signpost(LinkRel.author, "https://orcid.org/0000-0001-9447-460X")
        Signpost(LinkRel.item, "https://example.com/download.zip", "application/zip")
    )

    return response

Manual parsing of JSON-LD

If you have metadata in JSON-LD available, but it is not rendered as part of the response, you can still parse it and add the signposting links manually:

from django.http import HttpResponse
from django_signposting.utils import add_signposts, jsonld_to_signposts

response = HttpResponse("Hello World")
json_ld = {
    "@context": "http://schema.org/",
    "@graph": [
        ...
    ]
}
signposts = jsonld_to_signposts(json_ld)
add_signposts(response, **signposts)

Add signposts as HTML links instead of headers

In cases where you want to include signposting directly in the HTML response rather than as HTTP headers (for example because headers are overwritten by a proxy or something else), you can use the HtmlSignpostingMiddleware instead of SignpostingMiddleware.

This middleware automatically adds elements to the HTML section based on the detected signposting metadata and produces output similar to the one shown here:

<!DOCTYPE html>
<html>
 <head>
  (...)
  <link href="http://schema.org/WebSite" rel="type"/>
  <link href="http://schema.org/Dataset" rel="type"/>
  <link href="https://orcid.org/0000-0001-9447-460X" rel="author"/>
  <link href="https://creativecommons.org/licenses/by/4.0/" rel="license"/>
  <link href="https://example.com" rel="cite-as"/>
  <link href="https://example.com/download.zip" rel="describedby" type="application/zip"/>
  <link href="https://example.com/metadata.json" rel="describedby"/>
  <link href="http://example.com/image.png" rel="item" type="image/png"/>
  <link href="http://example.com/image2.png" rel="item" type="image/png"/>
 </head>
 ...
</html>

TODO

Add support for link sets
Add support for specifying profile extension attribute

License

Licensed under the MIT License.

Metadata

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