edge u201d refers to the connection between two event points i e its end points its domain is a finite non self intersecting open curve an edge has two end points and its length is greater than zero e a i a j denotes an edge that has a i and a j as its end points a u201c segment u201d is similar to an edge in that it is also a closed line it stores an upper end point and a lower end point let s a i a j denote a segment that has a i and a j as its end points let a i lt y a j denote that point a i is smaller than a j along the y axis similarly a i lt x a j denotes that point a i is smaller than a j along the x axis if a i lt y a j or a i y a j and a i lt x a j in the printer device coordinate scheme a i is the upper end point and a j is the lower end point a u201c segment pair u201d consists of two segments which intersect the sweep line and lie on opposite edges of a given region it indicates an area between two segments that is part of a gdi fill area for a particular metafile record or polygonal object a u201c segment pool u201d contains segments having a particular attribute e g color as inherited from the original input data i e the attribute of its related polygonal object multiple segment pools are maintained within the mc.