VODML, VODML-ID and names

[Laurent Michel]

Hello DM,

The purpose of this mail is multiple
- Stop blurring the "MIVOT: fully qualified attribute names" thread with considerations on VODML
- Specifying the roles of both VODML-IDs and names
- Assess their impact on the recommended models

Each VODML element has a name and a VOMDL-ID.
 From the standard point of view:
- Both must comply with a regexp.
- names must be unique within their enclosing type or package (section 4.1.2)
   in simpler word: we cannot have 2 attributes with the same name.
- VODML-IDs must be unique within the document (section 4.1.1)
- nothing is said about the way to build these 2 fields
- nothing is said about the way they are connected to each other.

The reason for having different uniqueness rules is that VODML documents are built as flat lists  of elements that has to be put 
together by solving references (VODML-REF) against VOMDL-IDs.
For this reason :
- All referable elements must have a VOMDL-ID unique within the document.
- Non referable elements (e.g. attributes) could live without  VODML-ID

The problem now is that the VODML-IDs are here and everywhere and removing them would require an upgrade of the VODML schema and 
  also of all the models based on VODML (PhotDM, Meas, Coord, Provenance) since those models directly refer to VODML-IDs (see 
enclosed screenshot from Meas).

As this is not a blocking issue for MIVOT or the incoming high level models (Cube, MANGO) either, it would be wise not to press 
on the Replay button of the last 8 years history.
Anyway I won't be the one who will have to manage this.


Laurent
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