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Internationalisation issue in IMSC - xml:lang usage

From: John Birch <John.Birch@screensystems.tv>
Date: Tue, 5 Nov 2013 11:47:19 +0000
To: Nigel Megitt <nigel.megitt@bbc.co.uk>
CC: Andreas Tai <tai@irt.de>, Frans de Jong <dejong@ebu.ch>, public-tt <public-tt@w3.org>
Message-ID: <0981DC6F684DE44FBE8E2602C456E8AB014B2A937D@SS-IP-EXMB-01.screensystems.tv>
Hi Nigel,

Below is a paragraph or two with my key points and proposed resolution about xml:lang and IMSC. Please alter, submit etc. as you see fit.

I have deep concerns about the constraints in IMSC on the use of xml:lang which I feel are completely contrary to the accepted use (and recommended best practise) of this attribute from the xml standard. The IMSC document states in section 4.4 Language that “All instances of the xml:lang attribute within a subtitle document SHALL have identical values.”

In the W3C document “Best Practices for XML Internationalization” [http://www.w3.org/TR/xml-i18n-bp/#AuthoringTime] published by the W3C Working Group on 13 February 2008 (over 5 years ago and without subsequent amendment or correction), section 3 “When Authoring XML Content” states that

“Authors of XML content should consider the following best practices:”.

Best Practise: Specifying the language of content             Use xml:lang (or its equivalent in your schema) on the root element of the document, and on each element where the language of the content changes. (my emphasis)

Clearly the best practise is to use xml:lang to correctly identify the language of any element within a document when it differs from the surrounding elements.

This best practise advice is further reinforced by another document from the W3C: xml:lang in XML document schemas [http://www.w3.org/International/questions/qa-when-xmllang] in the section “When to use xml:lang”.

Content directly associated with the XML document (either contained within the document directly or considered part of the document when it is processed or rendered) should use the xml:lang attribute to indicate the language of that content. xml:lang should be reserved for content authors to directly label any natural language content they may have.

xml:lang is defined by XML 1.0 as a common attribute that can be used to indicate the language of any element's contents. This includes any human readable text, as well as other content (such as embedded objects like images or sound files) contained by the element in which it appears. The xml:lang value applies to any sub-elements contained by the element. It also applies to attribute values associated with the element and sub-elements (though using natural language in attributes is not best practice). The value of the xml:lang attribute is a language tag defined by BCP 47.

I believe the IMSC document should be corrected to accurately reflect the established guidelines.

Best regards,

John Birch | Strategic Partnerships Manager | Screen
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From: Nigel Megitt [mailto:nigel.megitt@bbc.co.uk]
Sent: 31 October 2013 16:50
To: John Birch
Cc: Andreas Tai; Frans de Jong
Subject: Internationalisation issue re IMSC

Hi John,

At this afternoon's TTWG meeting I mentioned that the EBU may raise an issue on the IMSC draft relating to internationalisation, i.e. the restriction on xml:lang and the constraints on code pages. It appears that we have an opportunity to discuss this at TPAC the week after next, and that we can call on a W3C Internationalisation (i18n they call it, for short) expert Richard Ishida to join the meeting in person and help with the issue. It would be good to give him as much notice as possible however.

As you've been one of the more vocal members of our group would you like to draft (or edit from previous emails) the key points of the issue and possibly propose a resolution, which we (actually you are able to do it but I can do so on behalf of the EBU XML Subs group) can then raise on the tracker, to inform Richard and give a placeholder for the agenda?

Kind regards,



Nigel Megitt
Lead Technologist, BBC Technology, Distribution & Archives
Telephone: +44 (0)208 0082360
BC4 A3 Broadcast Centre, Media Village, 201 Wood Lane, London W12 7TP



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Received on Tuesday, 5 November 2013 11:47:50 UTC

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