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Response to your LC Comment -2389 on Media Ontology spec

From: Thierry MICHEL <tmichel@w3.org>
Date: Wed, 29 Sep 2010 08:53:00 +0200
Message-ID: <4CA2E24C.1020402@w3.org>
To: tomac@google.com
CC: "public-media-annotation@w3.org" <public-media-annotation@w3.org>
Dear Thomas,

The Media Annotations Working Group has reviewed the comments you sent 
[1] on the Last Call Working Draft [2] of the Ontlology for Media 
Resource 1.0 published on 08 June 2010.
Thank you for having taken the time to review the document and to send 
us comments.

The Working Group's response to your comment is included below.
Please review it carefully and *let us know by email at 
public-media-annotation@w3.org if you agree with it* or not before 
deadline date [09-oct-2010].
In case of disagreement, you are requested to provide a specific 
solution for or
a path to a consensus with the Working Group.
If such a consensus cannot be achieved, you will be given the 
opportunity to raise a formal objection which will then be reviewed by 
the Director during the transition of this document to the next stage in 
the W3C Recommendation Track.


For the Media Annotations Working Group,
Thierry Michel,
W3C Team Contact

2. http://www.w3.org/TR/2010/WD-mediaont-10-20100608/

MAWG Resolution:

1) Subtitles

Concerning external subtitles, using ma:relation is the correct approach 
as in your example. The identifier attribute contains the URL of the 
subtitle file, and the relation type qualifies it as a subtitle 
relation. The value should be a URI, but could also be a string. It is 
recommended to use a controlled vocabulary for the type of the relation.

Embedding of subtitles is not a use case that we considered, however it 
is possible. The mechanism we use to specify timed metadata is to 
specify fragments identified by Media Fragment URIs [1] and then 
describe annotations of these fragments.

To summarize, we see these 3 options for dealing with subtitles:

- Link to external subtitle file using ma:fragment, with type subtitle 
and a Timed Text Markup Language (TTML) [2] or WebSRT [3] file as target.
- Subtitles can be embedded in a media file, in which case they can be 
described as a track media fragment using ma:fragment and Media Fragment 
URIs [1].
- Subtitles could be embedded by using ma:title with a type qualifier 
for subtitle. A list of time media fragments is defined and each 
fragment is annotated using ma:title.

Although the last option is a way of embedding subtitles that is not a 
use case we considered. We expect that in most cases a dedicated format 
such as TTML or WebSRT will be used for the subtitles and referenced.

2) Semantic annotation

As described above, time based annotations are a possible. Currently, 
two cases are covered by the spec:

- use ma:description for a textual description of the media resource (or 
a fragment)
- use ma:relation to link to a RDF file or named graph containing the 
annotation for the media resource (or fragment)

There is currently no solution for embedding a set of triples into one 
of the ma:* properties. We understand that might be useful and have 
started discussion with the Semantic Web Coordination Group about a 
solution for this problem (see thread starting at [3]). The summary of 
the discussion is: Named graphs could be a solution to this issue, but 
there is no standard syntax for expressing them, to which our 
specification could refer. Such a syntax might find its way into RDF 
2.0. As no other applicable solution emerged in the discussion, we 
decided to exclude the embedding of triples into ma:* elements until a 
standard syntax for named graphs is available.

[1] http://www.w3.org/TR/2010/WD-media-frags-20100624
[2] http://www.w3.org/TR/2010/CR-ttaf1-dfxp-20100223/
[3] http://www.whatwg.org/specs/web-apps/current-work/#websrt-0
Received on Wednesday, 29 September 2010 06:53:55 UTC

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