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A diagonal can refer to a line joining two nonconsecutive vertices of a polygon or polyhedron

Only a Diagonal of 2D Polygon considered here.

In this case the UML model elements are adorned with mathematical notations indicating the author's understanding of the sentence, which are not explicit in the source text.

Note the UML "Object Diagram" exploring a possible diagonal of a polygon. The simple composite structure features of UML™ composite structures and the more advanced deep structure and value state modelling possibilities of SysML Internal Block Diagrams (IBDs) provide more possibilities for representing object-llike information gleaned from source text, and stronger binding to Properties of domain Classes.