definition "x has gene product of y if and only if y is a gene (SO:0000704) that participates in some gene expression process (GO:0010467) where the output of that process is either y or something that is ribosomally translated from x"
We would like to be able to express the rule: if t transcribed from g, and t is a noncoding RNA and has an evolved function, then t has gene product g.