Figure 2
From: POEM, A 3-dimensional exon taxonomy and patterns in untranslated exons
The dimensions of exon categories. Frame (a) identifies the four types of intronless exons. The digit before the period indicates an intronless gene with only one "exon". The dimension value following the period represents which CDS boundaries are spanned. Frame (b) states the 3 parts of a regional exon. The leftmost value states the exon's position with respect to all other exons in the same gene; the middle value indicates the exon's position within its region (which is represented by the rightmost value). Frame (c) represents a CDS-oriented exon, by first stating its global position followed by an indicator of which CDS boundaries are spanned.