y expresses x if and only if there is a gene expression process (GO:0010467) that occurs in y, and one of the following holds: (i) x is a gene, and x is transcribed into a transcript as part of the gene expression process (ii) x is a transcript, and x was transcribed from a gene as part of the gene expression process (iii) x is a mature gene product (protein or RNA), and x was translated or otherwise processed from a transcript that was transcribed as part of the gene expression process.