Proposed Language for #111 - Revision 5

The following is revision 5 of my proposed text. I have added language to
address the comments received today from Mike and Nigel. Revisions (from
what we reviewed in today's meeting) are highlighted.

Add to Section 3:
IMSC Processor. A *Processor* that supports one or both IMSC Profiles.
Single-Profile IMSC Processor. An IMSC Processor that supports one and only
one of the profiles defined in Section 5, namely, the Text Profile or the
Image Profile. Multiple-Profile IMSC Processor. An IMSC Processor that
supports both of and only the profiles defined in Section 5, namely, both
the Text Profile and the Image Profile.

Compatible Profile. A non-IMSC profile with which IMSC is expressly
designed to be compatible for the purpose of enhancing content
interoperability. A Document Instance declared or determined to be
associated with a Compatible Profile does not violate IMSC defined content
constraints with respect to one of the profiles defined in Section 5.
Note: The profiles defined by [EBU-TT-D], [ST2052-1], and [ttml10-sdp-us]
are examples of Compatible Profiles.
Create a new Section 5.4, entitled *Profile Specification and Processing*:

[profile specification]

The ttp:profile attribute SHOULD be present on the tt element and equal to
the designator of the IMSC1 profile to which the document conforms; unless
the document also conforms to [EBU-TT-D], in which case the ttp:profile
attribute SHOULD NOT be present on the tt element, and instead the
designator of the IMSC1 profile to which the document conforms and the URI
"urn:eebu:tt:distribution:2014-01" SHOULD each be carried in an
ebuttm:conformsToStandard element as specified in [EBU-TT-D].

[profile defaulting]
A Single-Profile IMSC Processor SHALL process a Document Instance in
accordance to the single profile which it supports. If a profile is
determined by [profile specification] and its value is not equal to the
profile designator associated with that single supported profile and is not
a Compatible Profile with respect to that single supported profile, then
the Document Instance MAY be considered incompatible with that Processor
and subject to abort processing. If no profile is determined by [profile
specification], then the Document Instance SHOULD be tentatively considered
to be compatible with that Processor and subject to normal processing.
A Multiple-Profile IMSC Processor SHALL process a Document Instance in
accordance to one of its supported profiles. If a profile is
determined by [profile
specification] and its value is not equal to the profile designator
associated with any of the supported profiles and is not a Compatible
Profile with respect to any of the supported profiles, then the Document
Instance MAY be considered incompatible with that Processor and subject to
abort processing. If no profile is determined by [profile specification],
and if no external profile metadata is provided by the Document Interchange
Context, then the Document Instance SHOULD be tentatively considered to be
compatible with the Text Profile and subject to normal processing as such.

In order to avoid the invocation of this [profile defaulting] procedure,
content authors and interchange agents SHOULD specify the profile that
applies to a Document Instance, by means of either the [profile
specification] procedure or external profile metadata, or both. If both
internal and external profile metadata is provided and if there is a
disagreement between the two designated profiles, then the external profile
metadata takes priority.
Note: A Document Interchange Context can obtain external profile metadata
by multiple means, including but not limited to: profile parameter data
provided by a content container or envelope, using a pre-processor that
attempts to guess the applicable profile, etc.

Note: If a Document Instance is considered compatible with a Processor, but
is determined to be incompatible, then normal processing may be aborted. As
an alternative, a Processor is permitted to restart processing with the
Image Profile as the default profile in case an incompatibility is detected
and the [profile defaulting] procedure was previously used to select the
Text Profile.

Note: The determination and processing of the profile of an arbitrary TTML
Document Instance that is not compatible with either Profile defined herein
is outside the scope of this specification.

Modify Section 6.10 #profile entry to replace the first paragraph

"The ttp:profile attribute ..."

with the following:

"The constraints and recommendations specified by [profile specification]
(see §5.4 above) apply."