(0) You said “I don&#x27;t mean directed graphs, only vertices and edges.” But a syntax tree, viewed as a graph, is very much a directed one - the relation between a parent node and its children is asymmetric.<p>(1) A syntax tree isn&#x27;t the same thing as a computation. Of course, you can produce computations by interpreting syntax trees, but: (a) It&#x27;s perfectly possible for two distinct syntax trees to produce the same computation. [Say, by renaming all variables.] (b) It&#x27;s also perfectly possible that interpreting the same syntax tree twice will produce completely different computations! [Say, if your language isn&#x27;t pure.] Unsurprisingly, a syntax tree is a representation of <i>syntax</i>, not computation.<p>(2) Yes, I&#x27;m disappointed, because I expected your observation that “every computation (...) is isomorphic[sic] to some graph” to provide more insight than it turned out to.<p>Edit: Turned paraphrasing into literal quote.