In the interest of research and all other things persuant to the ChronocidalManiac. Version 0.1 of the MetaModel for the GalacticModelingLanguage:
  _____
 |     |
 | Box |__________
 |_____|0..1      |
    |2            |
    |             |
  __|*_         __|1_
 |     |       |     |
 |Line |_______|Label|
 |_____|0..1  *|_____| 
 
--DaveElton & DavidBates et al.

Now, let the debate about the cardinality of Box vs. Label begin

''Too complicated and too verbose.  All you'll ever need can be built from this metamodel:''

  _____
 |     |
 |Thing|______
 |_____|      |
    |         |
    |         |
    |         |
    |_________|


''Box, Line and Label are all instances of Thing.  In English:''

'''Things have things.'''

This sort of unified-theory minimalism arises in all seriousness sometimes, e.g. in the elegant Interviews GUI framework, everything was a box. It's also reminiscent of pure OO languages, where everything is an object.
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Or, in abbreviated UmlAsciiArt

  Diagram
    [name,date,author,new(),save(),delete()]
  Box *Diagram@
    [X,Y,width,height,weight,borderColor,fillColor,create(),draw(),delete()]
  Line *Box@
    [X1,Y1,X2,Y2,weight,borderColor,fillColor,create(),draw(),delete()]
  Label *Box@,*Line@
    [name,fontType,foreColor,backColor,X,Y,create(),draw(),delete()]
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CategoryHumor HaHaOnlySerious GalacticModelingLanguage