[MEI-L] Coordinate system confusion

[Daniel Alles]

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