SHACL: A Description Logic in Disguise

SHACL is a W3C-proposed language for expressing structural constraints on RDF graphs. In recent years, SHACL's popularity has risen quickly. This rise in popularity comes with questions related to its place in the semantic web, particularly about its relation to OWL (the de facto standard for expressing ontological information on the web) and description logics (which form the formal foundations of OWL). We answer these questions by arguing that SHACL is in fact a description logic. On the one hand, our answer is surprisingly simple, some might even say obvious. But, on the hand, our answer is also controversial. By resolving this issue once and for all, we establish the field of description logics as the solid formal foundations of SHACL.