Convert to run from IIIF manifest with navDate

[tomcrane]

This timeline predates the IIIF Presentation API (or at least, Wellcome's use of it).

However, the data model (label, description, images, image services, dates) maps nicely to a IIIF manifest, or a collection. It would be good to drive the timeline from a manifest or collection, to give a different/alternative/interesting rendering of IIIF material that has date info available.

The is useful because lots of people already have the material as IIIF, they don't need to do too much to manage new timeline data. Any ad hoc IIIF resources, for storytelling can be stored in a Presentation API server if necessary. For example a IIIF Collection created specifically to sequence a set of works for a blog post.

I would add an extra, optional, timeline-specific service to provide the "loose" date format the timeline supports (e.g., Romans leave Britain: 410 CE) for which IIIF navDates (“YYYY-MM-DDThh:mm:ssZ”) are inappropriate. Lots of people would be be happy driving a timeline off of navDates only, so if that's all there is use that; otherwise, get the more historical friendly date format, without misleading precision - provide this as a service extension.

Use cases:

1. Display of newspaper issues, periodicals, etc - likely to already to have navDate anyway, and be in Gregorian calendar to boot. Show highlighted front pages from a particular journal. Easy win.
2. IIIF Collection of works by particular author/creator - see timeline of published novels; paintings by artist over career, albums, etc (David Bowie albums with covers on timeline)
3. Archival items over the course of a career; thumbnail service on item-level manifest gives appropriate highlight (see also https://groups.google.com/forum/#!topic/iiif-discuss/2pKcLuxic4I); trace emergence of ideas from an ad-hoc IIIF collection (links between manifests/canvases as hotlink annotations to reconstruct correspondence). Trace emergence of scientific ideas through correspondence over time.
4. other cool stuff. Any collection, manifest or canvas level search results returned as IIIF collection (see IIIF Discovery) could be rendered on a timeline if date info available.