Re: [sdw] WebVMT: Investigate better out-of-band link handling (#1107)

Thanks for your feedback.

I'm not sure I understand what you mean by:

> it does not give you a way to assemble these files together unless you already know that all of these files exist

If we know that one file exists, there are three possibilities:

a. Starting from an HTML file, I agree that the media and VMT files are already identified in HTML, unless they're loaded by the client. The link information is duplicated in the VMT file and the HTML takes precedence. In the static HTML case there is redundancy, and for dynamic HTML (e.g. from a PHP script) the VMT file includes the required information to construct the HTML.

b. Starting from a media file, there's no embedded information so the media file is unaware of the VMT file and ignores it. This allows metadata to be added without modifying existing media, which is important for certain use cases, e.g. [YouTube demo](http://webvmt.org/demos#youtube), [Police Evidence](http://w3c.github.io/sdw/proposals/geotagging/webvmt/#policeevidence).

c. Starting from the VMT file, the media block identifies the linked media. I acknowledge that this could be achieved with file naming conventions in most cases, though I think that would be weak design, and I don't see how it would work for the [YouTube use case](http://w3c.github.io/sdw/proposals/geotagging/webvmt/#helloyoutube) as the media file is not accessed directly and its name is unknown. Including explicit link (i.e. url) details leaves no margin for error, which I believe is important for an XML variant of the data model, to ensure correct validation.

@lvdbrink: Can you offer a comment on this XML validation issue?

> it wouldn't provide a solution for all use cases

Although I hadn't considered embedding VMT content within the media file, the media block could point to the current file in this case.

Perhaps I've misunderstood. Please outline a use case where the media block would not provide a solution.

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Received on Thursday, 31 January 2019 12:11:25 UTC