Re: Unique ids in MusicXML 3.1 and beyond

Hi Adrian,

To clarify the original point, the uid is just like a unique address for each item in a score, so any document external to the MusicXML can unambiguously refer to any item in the score, even when the score is changed, until the item is deleted

The problem with bars[B].parts[P]... as an address is that it is not robust in the face of modifications to the XML. ie if you add a part or a bar then indices B and P do not point to the same place, and you normally cannot detect the failure!
However if you use global uids they remain valid until the target object is deleted, and then you can detect when it has failed, as long as ids are never reallocated. (An interesting problem is how to ensure that.)

James Sutton
Dolphin Computing
http://www.dolphin-com.co.uk <http://www.dolphin-com.co.uk/>
http://www.seescore.co.uk <http://www.dolphin-com.co.uk/>
http://www.playscore.co <http://www.dolphin-com.co.uk/>




> On 8 Sep 2017, at 15:28, Adrian Holovaty <adrian@holovaty.com> wrote:
> 
> On Fri, Sep 8, 2017 at 4:01 PM, James Sutton <jsutton@dolphin-com.co.uk <mailto:jsutton@dolphin-com.co.uk>> wrote:
> Here is a couple of cases:
> 
> 1. If any program (eg OMR engine) needs to output non-MusicXML information (eg bounding-boxes of items)  then it could be passed via another channel (XML, JSON, text, ..), cross-referencing by uid
> 
> 2. a) If a conductor taps a note on her tablet, the note could be highlighted on all the players' tablets by passing a uid. The MusicXML might be generated by a completely independent program which outputs uids.
> 
>  b)  the note might be changed, or a notation might be removed or corrected
> 
> This does open a general way of referring to elements in a MusicXML file and for passing any information about elements which is not catered for in the MusicXML format.
> 
> For these use cases, it would be nice to have a general "selector" API for music notation in general — not just MusicXML, but any symbolic common Western notation across any app.
> 
> Joe has brought up this idea in the past, and I think it's a great one. Imagine something like this, to select the second beat of the first voice in the first bar of the first part:
> 
>     bars[0].parts[0].voices[0].beats[1]
> 
> It seems inelegant to shoehorn such a thing into MusicXML via a change to the way IDs work, but I admit I don't understand your original proposal, despite having read it a few times. :-/
> 
> Adrian
> 
> --
> Adrian Holovaty
> Soundslice: https://www.soundslice.com/ <https://www.soundslice.com/>
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