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RE: Fall back strategy for manifest

From: Domenic Denicola <domenic@domenicdenicola.com>
Date: Mon, 27 Jan 2014 19:58:35 +0000
To: Marcos Caceres <w3c@marcosc.com>, "www-tag@w3.org" <www-tag@w3.org>
Message-ID: <0ffc9ac3c5714a10be86dd2f86becff9@BN1PR05MB325.namprd05.prod.outlook.com>
Hi Marcos!

4 ("Don't redefine stuff that is in HTML") certainly sounds appealing at first glance. Could you tell us more about possible problems with that approach? I assume it doesn't work out perfectly...

Also, could you clarify the model with regard to the manifest and the HTML file(s)? It sounds like there's an assumption that there's a single important HTML file ("index.html" perhaps) where the <meta> and <link> tags could live. What about multi-page apps? What if they defined conflicting <meta> data?

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From: Marcos Caceres <w3c@marcosc.com>
Sent: Monday, January 27, 2014 14:33
To: www-tag@w3.org
Subject: Fall back strategy for manifest

Hi TAG,
I'm currently working on standardizing this manifest thingy [1] that allows devs to define metadata for their Web apps using JSON. Example metadata includes the application's name and icons, plus the supported orientations and other little things for now.

The problem I'm having is that HTML already provides this capability through <meta> and <link> elements. So, ignoring the fact that I'm (mostly unnecessarily) redefining stuff that is already in HTML, the question I have is: what would be a web friendly way to handle when both the manifest and the HTML define metadata about the web application?

The options, I guess, are:

1. Manifest wins: if valid metadata is provided in the manifest, ignore what is in the HTML. Otherwise, fall back to the HTML.
2. HTML wins: ignore anything in the manifest that is already in the HTML document. Use the manifest to fill the gaps.
3. Manifest and HTML should be combined - take the union of both and, in case of conflict, use that with either the stuff in the manifest winning or the stuff in the HTML winning.
4. Don't redefine stuff that is in HTML.
5. ???

I'm currently specifying 1. So, for example, if there are valid icons found in the manifest, then those are used and the ones in the HTML document are ignored. However, if the application's name is not in the manifest (or it was an invalid type), the user agent falls back to HTML.

Any guidance would be appreciated.

[1] http://manifest.sysapps.org/

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Marcos Caceres
Received on Monday, 27 January 2014 19:59:23 UTC

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