Harvestable streams (Change Discovery)

To let aggregators, portals, and search indexes discover what changed since they last looked, djiiif can serve a IIIF Change Discovery 1.0 activity stream — the IIIF equivalent of a sitemap + RSS for your manifests. It’s a natural fit for Django: the stream is just a queryset ordered by a modified timestamp, paginated.

Configure the source

Point IIIF_ACTIVITY_SOURCE at a callable (or a dotted-path string) that yields one entry per resource, in ascending end_time order:

settings.py

IIIF_ACTIVITY_SOURCE = "myapp.iiif.activities"

myapp/iiif.py

def activities():
    for photo in Photo.objects.exclude(image="").order_by("modified"):
        yield {
            "object_id": f"https://example.org/iiif/{photo.slug}/manifest",
            "end_time": photo.modified,          # an aware datetime
        }

Each entry is a plain dict (or an Activity dataclass) with:

Field	Default	Meaning
object_id	—	the manifest (or collection) URL
end_time	—	the modification timestamp (aware datetime or ISO 8601 string)
type	"Update"	the activity type ("Update" or "Create")
object_type	"Manifest"	"Manifest" or "Collection"

The endpoints

With the URLconf mounted, the stream is served at:

• /iiif/activity/collection — the OrderedCollection entry point. Harvesters start here and follow the first/last/next links.

• /iiif/activity/page/<n> — the OrderedCollectionPages.

Page size comes from IIIF_ACTIVITY_PAGE_SIZE (default 100). Unset IIIF_ACTIVITY_SOURCE ⇒ the activity URLs 404.

Performance & ordering

Returning a queryset (rather than a generator) lets pages slice lazily in the database — the recommended shape for large collections. A generator source is materialized per request, which is fine for thousands of images.

Important

Ordering is trusted, not re-sorted — your source must yield ascending by end_time. (Re-sorting would defeat lazy queryset slicing.)

Conformance level

This is level 1 (Update/Create activities with timestamps — enough for incremental harvest). Delete tracking (level 2) would require a persisted tombstone log and is future work.