The colored directed graph representing a gene structure. The represented gene structure, induced by compositions, is composed by 6 genomic exons: A, B, C, C', D, E. Dashed edges represent noncoding regions, bold edges represent regions included into all the gene isoforms, and the remaining normal edges represent regions that are both coding and noncoding (i.e. are included into some gene isoform and are retained as a part of an intron into some other isoform). For clarity, we indicated an exon with a curve above the graph, and an intron with two connected segments below the graph. Observe that C and C' are competing exons, while exons B and D are cassette exons.