[MEI-L] Coordinate system confusion [and terminology]

Roland, Perry D. (pdr4h) pdr4h at eservices.virginia.edu
Sat Jul 8 21:55:11 CEST 2017 

If there's support from the community, I'm fine with changing "vu" to "hs".  If we're going to break it, let's break it now.  
In the schema and Guidelines, it's a simple search-and-replace. Changes to existing markup can be built into the version 3 to version 4 XSLT.  But I can't speak to changes to Verovio and other MEI-based software, so if there are objections from developers, speak now please.

--
p.

> -----Original Message-----
> From: mei-l [mailto:mei-l-bounces at lists.uni-paderborn.de] On Behalf Of Byrd, Donald A.
> Sent: Saturday, July 08, 2017 3:34 PM
> To: Music Encoding Initiative <mei-l at lists.uni-paderborn.de>
> Subject: Re: [MEI-L] Coordinate system confusion [and terminology]
> 
> I understand the issue. But I think just saying "half-STEPS/diatonic steps" instead of "half-
> spaces/diatonic steps" and half-spaces (hs for short) instead of virtual units (vu for short)
> would do the job. No need to change the unit, just the term.
> 
> Thanks for listening! I'll shut up now.
> 
> --DAB
> 
> 
> On Jul 8, 2017, at 3:12 PM, "Roland, Perry D. (pdr4h)" <pdr4h at eservices.virginia.edu>
> wrote:
> 
> >
> > Don,
> >
> > Like I said before, changing MEI's unit of measurement from half-spaces/diatonic steps
> to spaces would break all existing markup and software.  Changing the markup is
> reasonably easy, but modifying software is another problem all together.  So, unless there's
> a HUGE outcry from the community, I'd prefer to leave things as they are.
> >
> > --
> > p.
> >
> >
> >> -----Original Message-----
> >> From: mei-l [mailto:mei-l-bounces at lists.uni-paderborn.de] On Behalf Of Byrd, Donald
> A.
> >> Sent: Saturday, July 08, 2017 2:48 PM
> >> To: Music Encoding Initiative <mei-l at lists.uni-paderborn.de>
> >> Subject: Re: [MEI-L] Coordinate system confusion [and terminology]
> >>
> >> Before my original suggestion is completely forgotten, I'd like to
> >> back up a little. Perry, you said
> >>>
> >>> I have trouble, as I think most folks would, with values like "2-1/2
> >>> half-spaces". I can
> >> live with "2-1/2 steps", but still prefer "2-1/2 vu".  We can/should
> >> define a "vu" in relation to diatonic steps though.
> >>
> >> Gould and Read  rarely if ever saying anything like "2-1/2
> >> half-spaces"; the example I gave, and what they actually say, is "2-1/2 SPACES".  And
> the fact the "spaces"
> >> terminology is used consistently by both in works intended for
> >> practical use seems like pretty good evidence that that terminology doesn't bother
> people much.
> >>
> >> Let's see, here's a random note in a random piece of music; I wonder how long its stem
> is?
> >> Ah, it extends all the way across three spaces and halfway across
> >> another! :-). It's a standard one-octave stem, with a length of 3 and 1/2 spaces.
> >>
> >> --Don
> >>
> >>
> >> On Jul 7, 2017, at 4:41 PM, "Roland, Perry D. (pdr4h)"
> >> <pdr4h at eservices.virginia.edu>
> >> wrote:
> >>
> >>> Yes, 1 vu = 1 diatonic step.  However, the phrase “diatonic step”
> >>> doesn’t actually appear in the definition –
> >>>
> >>> “A single vu is half the distance between the vertical center point
> >>> of a staff line and that
> >> of an adjacent staff line.”
> >>>
> >>> Even this definition occurs within the description of @vu.height.
> >>> This is definitely a
> >> place where the Guidelines could use some work.
> >>>
> >>> --
> >>> p.
> >>>
> >>>
> >>> From: mei-l [mailto:mei-l-bounces at lists.uni-paderborn.de] On Behalf
> >>> Of Craig Sapp
> >>> Sent: Friday, July 07, 2017 2:58 PM
> >>> To: Music Encoding Initiative <mei-l at lists.uni-paderborn.de>
> >>> Subject: Re: [MEI-L] Coordinate system confusion [and terminology]
> >>>
> >>>> We can/should define a "vu" in relation to diatonic steps though.
> >>>
> >>> Is that not already the case? Otherwise, I am confused...  In other
> >>> words 1vu = 1 diatonic
> >> step (such as E to F, or G-flat to A-sharp since the chromatic alteration does not
> matter).
> >>>
> >>>
> >>>
> >>> On 7 July 2017 at 20:45, Roland, Perry D. (pdr4h)
> >>> <pdr4h at eservices.virginia.edu>
> >> wrote:
> >>>
> >>> I have trouble, as I think most folks would, with values like "2-1/2
> >>> half-spaces". I can
> >> live with "2-1/2 steps", but still prefer "2-1/2 vu".  We can/should
> >> define a "vu" in relation to diatonic steps though.
> >>>
> >>> --
> >>> p.
> >>>
> >>>
> >>>> -----Original Message-----
> >>>> From: mei-l [mailto:mei-l-bounces at lists.uni-paderborn.de] On Behalf
> >>>> Of Byrd,
> >> Donald A.
> >>>> Sent: Friday, July 07, 2017 11:23 AM
> >>>> To: Music Encoding Initiative <mei-l at lists.uni-paderborn.de>
> >>>> Subject: Re: [MEI-L] Coordinate system confusion [and terminology]
> >>>>
> >>>> Sure. As I said, both Gould and Ross talk about "half spaces".
> >>>> --DAB
> >>>>
> >>>> On Jul 7, 2017, at 11:03 AM, "Roland, Perry D. (pdr4h)"
> >>>> <pdr4h at eservices.virginia.edu>
> >>>> wrote:
> >>>>
> >>>>>
> >>>>> Hi Don,
> >>>>>
> >>>>> You make a good argument for the term "staff-space" or "space".
> >>>>> However, MEI doesn't
> >>>> use this distance as its unit of measurement. Instead, MEI uses
> >>>> *half the distance* between adjacent staff lines, hence the need
> >>>> for a different term.  Perhaps "interline distance" and "virtual
> >>>> unit" aren't intuitive, but they
> >> accurately describe the situation, which "staff-space"
> >>>> or "space" do not.  Of course, we could start using the entire
> >>>> distance between staff lines as the unit, but that would mean
> >>>> changing all existing MEI
> >> markup and software.
> >>>>>
> >>>>> --
> >>>>> p.
> >>>>>
> >>>>>
> >>>>>> -----Original Message-----
> >>>>>> From: mei-l [mailto:mei-l-bounces at lists.uni-paderborn.de] On
> >>>>>> Behalf Of Byrd, Donald
> >>>> A.
> >>>>>> Sent: Tuesday, July 04, 2017 11:26 AM
> >>>>>> To: Music Encoding Initiative <mei-l at lists.uni-paderborn.de>
> >>>>>> Subject: Re: [MEI-L] Coordinate system confusion [and
> >>>>>> terminology]
> >>>>>>
> >>>>>> This reminds me of another source of coordinate system confusion,
> >>>>>> namely the term for the distance between staff lines. Verovio
> >>>>>> source code calls it a "double unit", and half that distance a
> >>>>>> "virtual unit" or "VU" or just
> >>>> "unit"; none of those terms is at all intuitive.
> >>>>>> Johannes calls it the "interline distance", which is much better,
> >>>>>> but rather long, and "half interline distance" is way too long
> >>>>>> (and clumsy). Well, look at Chapter 1 of _Behind Bars_. Her term
> >>>>>> is "stave-space", or just "space" for short; half that distance,
> >>>>>> of course, is a "half space". Ross' _Art of Music Engraving and
> >>>>>> Processing_, the only other book I know of that says much on the
> >>>>>> subject, just uses the
> >>>> term "space'. So, for example, both might describe a certain stem
> >>>> length as "2-1/2
> >> spaces".
> >>>>>>
> >>>>>> I submit "stave-space" (or "staff-space" on my side of the
> >>>>>> Puddle) as the full term and "space" for short are both the most
> >>>>>> standard and the
> >> best terms.
> >>>>>>
> >>>>>> --Don
> >>>>>>
> >>>>>>
> >>>>>> On Jul 4, 2017, at 11:16 AM, Daniel Alles
> >>>>>> <DanielAlles at stud.uni-frankfurt.de>
> >>>>>> wrote:
> >>>>>>
> >>>>>>> Thank you, Johannes, that really helped and made that clear. So
> >>>>>>> I can continue using the
> >>>>>> Edirom-coordinates for ulx etc.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> Zitat von Johannes Kepper <kepper at edirom.de>:
> >>>>>>>
> >>>>>>>> Dear Daniel,
> >>>>>>>>
> >>>>>>>> that's a real confusion, and we need to make it clearer in the
> >>>>>>>> guidelines. *Pixel* coordinates are always with the origin in
> >>>>>>>> the top left corner. *Music* coordinates, however, are always
> >>>>>>>> bottom up. @ulx and so on are always in pixel units, but @vo
> >>>>>>>> (vertical
> >>>>>>>> offset) is specified in interline distances (half the distance
> >>>>>>>> between two staff lines, or, in other words, the vertical
> >>>>>>>> distance between a C4 and a D4, or any other two adjacent
> >>>>>>>> notes). If you want to specify that a dynamic is written above
> >>>>>>>> its default position, it seems more natural that values go up (i.e., @vo="3").
> >>>>>>>> This means that for musical units the origin has to be bottom left.
> >>>>>>>> I know it's confusing in the guidelines, and we will address
> >>>>>>>> this at some point. If you don't mind, you're invited to
> >>>>>>>> prepare something on Git and submit a pull request ;-)
> >>>>>>>>
> >>>>>>>> Hope this helps,
> >>>>>>>> jo
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>> Am 04.07.2017 um 14:48 schrieb Daniel Alles
> >>>>>>>>> <DanielAlles at stud.uni-
> >>>> frankfurt.de>:
> >>>>>>>>>
> >>>>>>>>> Dear all,
> >>>>>>>>>
> >>>>>>>>> at the moment, I am a little bit confused about how MEI
> >>>>>>>>> defines its coordinate
> >>>> system:
> >>>>>> It is possible to add the attributes @ulx, @uly, @lrx and @lry to
> >>>>>> for example a surface, as written in part 12 of the Guidelines,
> >>>>>> which places the origin of the coordinate system in the upper
> >>>>>> left corner. All the examples in
> >>>> that part show that behavior, ulx/uly is always 0/0.
> >>>>>> This would correspond to the coordinate systems used in SVG and
> >>>>>> DOM and (which is what I use for my work) Edirom Editor. On the
> >>>>>> other hand it is written in part 22.3, that MEI uses a coordinate
> >>>>>> system in which "the y-axis points from bottom up". That would
> >>>>>> mean, that ulx/uly could never
> >>>> be 0/0.
> >>>>>>>>>
> >>>>>>>>> So now my questions: Is it sufficient to use the coordinates
> >>>>>>>>> like in the examples, with
> >>>>>> the origin in the upper left corner? Would that "override" MEIs
> >>>>>> original coordinate
> >>>> system?
> >>>>>> If not: Isn't the possibility to encode areas from top-left to
> >>>>>> bottom-right corners a semantic error in MEI, if the coordinate
> >>>>>> system is pointing from
> >>>> bottom-left to top-right?
> >>>>>>>>>
> >>>>>>>>> Best,
> >>>>>>>>> Daniel
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>
> >>>>
> >>>>
> >>> _______________________________________________
> >>
> >>
> >>
> >>
> >> _______________________________________________
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> 
> ---
> Donald Byrd
> Woodrow Wilson Indiana Teaching Fellow
> Adjunct Associate Professor of Informatics Visiting Scientist, Research Technologies
> Indiana University Bloomington
> 
> 
> 
> 
> 
> 
> 
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