[MEI-L] clef as milestone element

[TW]

2011/5/31 Andrew Hankinson, Mr <andrew.hankinson at mail.mcgill.ca>:
>
> <layout>
> ...
> <system id="1">
>  <systemstaff staffref="staff1">
>    <systemstaffdef clef.line= "2" clef.shape= "G">
>    <custos ... />
>  </systemstaff>
> </system>
> ...
> </layout>
>
> <staff n="staff1">
>  <layer>
>   ...
>   <sb systemref="1" />
>   ....
>
> I'm not sure what this would actually give us that we don't already (mostly) have. <systemstaff /> seems to exist only so we could define <systemstaffdef />.

I don't understand how the staff's position can be recorded without
having some kind of staff element in the layout tree?

> Since there is already a relationship between from <sb /> to the <system />, having a pointer the other way is unecessary (also, since multiple <sb />s could refer to the same system, you want the reference going this way).
>

You mean @staffref?

> Actually, we could just put the clef information on <system /> itself; e.g.,
>
> <system clef.line="3" clef.shape="C" />
>

I'm confused.  A clef is on the staff level, not the system level, right?

>
> We're not trying to replicate lilypond or any of the other notational drawing programs, so precise drawing information is "out of scope" for our purposes. We define the horizontal/vertical position of notes and anything else via the <facs /> system, where we draw bounding boxes around all the musical elements and then refer to them by ID. The bounding boxes give the absolute x/y coordinates (ulx uly), (lrx, lry). We're always doing it in reference to a page image, so we have a certain luxury there.
>

Then I'm misunderstanding something.  I thought the layout element
would be for *generating* a rendition of the music notation, not to
describe some facsimile?

> Since elements that are split between systems still belong to a staff, we don't have to worry about it. For example:
>
> <staff>
>   <layer>
>     <note xml:id="n1" />
>     <sb />
>     <note xml:id="n2" />
>   </layer>
>   <slur startid="n1" endid="n2" />
> </staff>
>

I'm thinking of the layout information.  A split element consist of
two or more separate graphical elements.  If positioning information
shall be recorded, then a single set of positioning attributes is not
enough.

Are we talking past each other?

Thomas