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[TTML2] Current draft - ttm:item concept

From: Andreas Tai <tai@irt.de>
Date: Thu, 11 Dec 2014 13:01:28 +0100
Message-ID: <54898798.9060302@irt.de>
To: Glenn Adams <glenn@skynav.com>, public-tt <public-tt@w3.org>
Hi Glenn,

 From my view the introduction of the “ttm:item element concept” needs 
more investigation. Currently I see problems a) with current validation 
mechanisms and b) a good change to encounter the same content in 
different parts of a TTML 2 document.

a) The semantic identity of a ttm:item element is defined by the value 
of the name attribute instead of the element name (e.g. there is a 
ttm:item element defined with the attribute name set to "creationDate" 
instead of a new element creationDate). In this scenario it is not 
possible to validate with XML Schema 1.0 that the content of <ttm:item 
name"creationDate">[Content]</ttm:item> conforms to the XML Schema 1 
DataType "date". Although this is possible with XML Schema 1.1 I do not 
see this as a validation option. The use of XML Schema 1.1 is not very 
wide spread yet and I do not know of any free parser that fully (!) 
supports XML Schema 1.1.

b) One use case of ttm:item is to integrate metadata that is already 
defined in other specification (e.g. in EBU Tech 3350/EBU-TT Part 1). It 
seems easier to me just to leave the metadata in the namespace where 
there are defined and integrate them by reference. Otherwise there is a 
good change that you have in two place (e.g. an ebuttm:creationDate 
element and a ttm:item element where the name is set to “creationDate”).

In general I very much appreciated the clear definition of the metadata 
section in the TTML 2 draft and the use of very helpful code examples to 
illustrate the usage of TTML vocabulary! Thanks for that!

Best regards,

Andreas

-- 
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Andreas Tai
Production Systems Television IRT - Institut fuer Rundfunktechnik GmbH
R&D Institute of ARD, ZDF, DRadio, ORF and SRG/SSR
Floriansmuehlstrasse 60, D-80939 Munich, Germany

Phone: +49 89 32399-389 | Fax: +49 89 32399-200
http: www.irt.de | Email: tai@irt.de
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Received on Thursday, 11 December 2014 12:05:25 UTC

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