Sharing a link for opening two or more Canvases

Use Case

I want to share a link to a colleague showing two similar works from two different collections. I want to compare pages from two different manuscripts and share a link to open both on the same view. I want to save my current workspace (open Canvases in the current viewer) for later use. I want to open my current workspace with another viewer.

Illustration of a possible way of visualizing two Canvases from different IIIF objects.

Implementation Notes

Some viewers already implement custom formats for exporting the current workspace for sharing or later use. The Content State API could be used for the same purpose, adding the advantage of direct loading of the workspace using a crafted link with the iiif-content query parameter. The multiple targets for a comparison view section describes a method for targetting two Canvases at the same time; each Canvas could be from a different Manifest.

For this purpose, we create an Annotation with motivation set to ["contentState"]. The value of the target property of the Annotation is a list containing the id of the Canvases and a partOf property with the id of the Manifests they belong to.

We can hence encode the Annotation as explained in the Content State encoding guidelines, and then pass the encoded value, using the iiif-content query parameter of the viewer landing page:

https://example.org/viewer?iiif-content=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

Restrictions

The Content State API does not define how the viewer should show the two Canvases. It only mentions:

“This data structure can be used by clients to load the resource required, present a particular part of the resource to the user.” https://iiif.io/api/content-state/1.0/#content-state

Viewers may show the Canvases side by side or decide to use different approaches (e.g. opening two browser tabs).

Example

In this example we want to compare two paintings of the Colosseum from two different Manifests. We can notice that the Colosseum painting of the first Manifest is in the second Canvas.

The Annotation will target the id of the two Canvases we want to compare and contain a reference to the two Manifests as shown in the example:

JSON-LD




The expected result should show the two Canvases of the two Manifest depicting the Colosseum.