AssetIdentifier extensions in v5 (2019-12-16)

[mikedo]

This new section has some problems:

1. Some sentences seem to require/forbid (using "shall" and "shall not") the presence of AssetIdentifier on Periods:

AssetIdentifier descriptor shall be used for distinguishing parts of the same asset within a multi-period MPD, hence it shall be used for main content and may be used for inserted content...If a Period has one-off semantics (i.e., an asset is completely contained in a single period, and its continuation is not expected in the future), the author shall not use asset identifier on these assets.

Is that the intent? Also for single Period programs how is that content identified (for other purposes)? If not, the normative language needs some clarification.

2. @schemeIdUri="urn:eidr" is not a valid URI and violates the syntax of RFC 7972 - the syntax after "urn:eidr:" is mandatory. One option is that the @schemIdUri could simply be set to the URI value of the EIDR and @value omitted. For example, schemIdUri="https://ui.eidr.org/view/content?id=10.5240/8CB2-351F-C046-AFE6-AB61-A". A bit unorthodox use of schemeIdUri/value but would work.

3. @schemeIdUri="urn:org:dash-if:asset-id:2014" is not a valid URI since "org" is an unregistered NID. See: https://www.iana.org/assignments/urn-namespaces/urn-namespaces.xhtml#urn-namespaces-1 Note that this URN was previously (and still) used in example 16 which needs to be fixed. Consider the tag: URI scheme (RFC 4151), e.g. ."tag:dashif.org,2014:schemeIdUri:asset-id" or register "dashif" as a URN NID and use "urn:dashif:asset-id".