Subject: [siprec] Metadata-04 - comments on section 4

From: "Elwell, John" <[email-masked]>
Date: Mon, 26 Sep 2011 11:22:56 +0200

(as individual)

1. "The Metadata model is a class diagram in Unified Modelling
   Language(UML). The model is a structure diagram that describes the
   structure of a recording's Metadata by showing the classes, their
   attributes, and the relationships among the classes."
The two sentences seem to be in conflict - is it a class diagram or a structure diagram?
Also, I believe the class diagram represents the structure of metadata in general, not the structure of metadata for a particular recording.

2. "Session Recording Client (SRC) MAY initiate the
   Recording Session."
This sounds like protocol to me. We should not have normative statements about initiating an RS in a section describing the metadata model.

3. "Here, Recording Session is a completely
   independent from the Communication Session that is being recorded at
   both the SIP dialog level and at the session level."
We should import definitions of CS and RS, and we should not need to explain the difference in this section.

4. "The metadata
   MUST be conveyed from SRC to SRS."
This too sounds like protocol.

5. "For example, if the call is transferred from
   one participant to another, then the SRC conveys the changes in the
   model ( In this instance change of participant and the properties of
   the new media stream) to the SRS."
This is probably a bad example. Although call transfer could be modelled as a change of participant in a CS, it could also be modelled as a change of CS (where one of the Participants is common). Can we pick an example where there is less scope for doing things differently (e.g., a Participant joins a conference)?

6. "Some of the metadata is not required to be conveyed explicitly from
   the SRC to the SRS, if it can be obtained contextually by the SRS.
   For instance, the timing of RS object changes(like Start / Stop time)
   may not be explicitly conveyed from the SRC to the SRS (The Date
   header in RS dialog SIP message provides the timing, but it is
   optional).  In such cases the time a change occurred may be assumed
   to be the same as the time when notification of the change is
   received by the SRS.  This is not true in cases where SRS requests a
   snapshot of metadata from SRC."
The first sentence seems OK, but I worry about the example that follows. It is getting into protocol, and the final sentence is certainly protocol. Perhaps all that is needed is to cite SIP/SDP as an example, e.g.:
"Some of the metadata is not required to be conveyed explicitly from
   the SRC to the SRS, if it can be obtained contextually by the SRS (e.g., from SIP or SDP signalling)."
Even that is perhaps not relevant for section 4 - and I see section 5, which might be more appropriate, already has something similar.

John

John Elwell
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