DIWG Response to the Timed Text (TT) Authoring Format 1.0 Use Cases and Requirements

The DIWG has reviewed the Timed Text (TT) Authoring Format 1.0 Use Cases and Requirements at 

http://www.w3.org/TR/2003/WD-tt-af-1-0-req-20030915/

The group has the following specific comments which we hope the TTWG will find helpful.

1) Section 1.2

In section 1.2 System Model, the term Transcoding is used to represent the tranformation between the timed text authoring fomat and the distribution format. Transcoding is one particular implementation that may be used during adaptation (definition at 
http://www.w3.org/TR/di-gloss/#def-adaptation). Others include selection among alternative representations. Indeed, selection within the authoring format is considered explicitly in Requirement R207. This is an important distinction. Transcoding essentially transforms between different representations of the same information. This is not always sufficient when dealing with devices with very different capabilities. Issues for authors associated with supporting a wide variety of devices are discussed in Authoring Challenges for Device Independence (see http://www.w3.org/TR/acdi/).

As the document under review is a set of use cases and requirements, DIWG feels it would be appropriate to acknowledge that transcoding is not the only transformation that might be applied to timed text. We suggest that section 1.2 and Figure 1 be updated to include alternative transformations as well as transcoding. It would probably be sufficient to lablel one of the boxes in the figure as Transformation rather than Transcoding. This would have the benefit of making explicit in the figure the statement about use of the proposed new format as a distribution format.

For information, DIWG maintains its Glossary (http://www.w3.org/TR/di-gloss/) for general use. We welcome other group's use of the definitions that it contains. The glossary is organised to support future revisions while maintaining earlier versions of definitions for reference by older documents. Details of how to use the glossary and of how it is maintained are contained within its appendices. There is also a description of why it is maintained as a working draft. A number of translations are underway.

2) Requirement R109 Transformability

Requirement R109, the list of legacy formats covers transformation to legacy formats. DIWG feels that it might be useful to mention adaptation in the context of this requirement. In addition, the list of legacy formats to be supported appears to be informative but might be read as normative. A normative list might be more appropriate for a requirements document.

3) Use of XSL-FO

The document makes heavy use of terminology from XSL and in particular XSL-FO. It would be useful to add a statement about whether the use of XSL-FO for styling has actually been assumed. If there are no such assumptions, it would be useful to add some reassurance that styling will be possible using other mechanisms, particularly CSS. This is potentially important to manufacturers of mobile devices, interactive television systems and other devices with limited resources. The 'footprint' of software that such manufacturers need to provide to support W3C recommendations is a constant challenge given the restricted resources available to them.

4) Normative or Informative Lists

Finally, DIWG also felt that would be helpful if appropriate statements could be added defining whether or not the various sets of enumerated values, for items such as styles, is intended to be normative or informative. DIWG assumes that these are intended to be normative.

Best Wishes

Rhys Lewis
Chair Device Independence Working Group &
Director of Software Architecture
Volantis Systems Ltd
1 Chancellor Court
Occam Road
Surrey Research Park
Guildford 
Surrey GU2 7YT
United Kingdom

Received on Thursday, 20 November 2003 10:14:06 UTC