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ISSUE-156 (semantics of missing #feature): semantics of missing #feature [DFXP 1.0]

From: Timed Text Working Group Issue Tracker <sysbot+tracker@w3.org>
Date: Wed, 15 Feb 2012 12:52:10 +0000
Message-Id: <E1RxeLC-0000qF-8a@tibor.w3.org>
To: public-tt@w3.org
ISSUE-156 (semantics of missing #feature): semantics of missing #feature [DFXP 1.0]


Raised by: Sean Hayes
On product: DFXP 1.0

It has been noted that there is an ambiguity in the way the profile work
A feature set is created in the following way:

The collection of features and extensions of a profile are determined according to the following ordered rules:

initialize the features and extensions of the profile to the empty set;

if a use attribute is present, then augment the profile with the set of features and extensions specified by the referenced baseline profile;

for each ttp:feature and ttp:extension element descendant of the ttp:profile element, using a post-order traversal, merge the specified feature or extension with the features and extensions of the profile, where merging a feature or extension entails replacing an existing feature or extension specification, if it already exists, or adding a new feature or extension specification, if it does not yet exist in the profile;

This process may result in a profile where some features are not mentioned at all. I tis not clear in such a case what the semantics should be, for example whether the missing features are optional or prohibited. As the feature mechanism does not provide a mechanism for prohibiting a feature being processed, and this is a semantic that some groups would like to express, they have adopted this interpretation. We should discuss whether missing implies must not process, in addition we should consider an explicit prohibited value.

We should also consider what it means to apply a profile to players, as opposed to documents.
Received on Wednesday, 15 February 2012 12:52:11 UTC

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