Outside of computer science, semantics is the providence of philosophy, where we talk about what we mean when we talk, as well as ontology (what there is to know) and epistemology (how we know it). The nice thing about computer science is that, in contrast to philosophy, we can establish whether different representations make a computational difference. That's what makes what we do engineering/science. In this paper, the author distinguished the meaning of semantics (in programming) from ontologies and logics.