Re: A question on RWPM: why the 'metadata' tag?

>
> So what's the progression direction if the collection says ltr and if
> the specific resource says rtl and has more than one page? IMO, that
> example alone clearly requires an importance order to be specified, the
> directions are conflicting.


As Laurent pointed out, this is the progression direction between resources.

On iOS for instance, we have what we call a triptych view:

|  Webview 1  |  Webview 2  |  Webview 3  |

We use this information to decide what goes in the first and third webviews:

   - 2 always shows the current resource
   - with ltr, 1 is the previous resource and 3 is the next one
   - with rtl, 1 is the next resource and 3 is the previous one

This is useful to create a better UX:

   - we can use the native swipe/drag between webviews
   - we can also prerender content in the background

I've seen similar takes on this using iframes as well on the Web, for
instance in Overdrive Read or Google's AMP viewer.
If browsers implement native support for Web Publications along with
dedicated gestures and/or UI elements, this could serve a similar goal. For
example, an enhanced reader mode could offer the ability to swipe or tap
between resources of a Web Publication.

If the content of each resource is paginated or scrolled horizontally, I
agree that there's potentially a "less than optimal UX" if the resource
says ltr and the progression direction of the collection is marked as rtl.
But that information is necessary for a number of user agents and as
always, this is collection level information which doesn't conflict with
resource level stuff.

Both the W3C WP manifest and RWPM are all about expressing information
about collections. This is quite different from the Web App Manifest, where
the focus is mostly on presenting information for the installation phase.