Abstract : Finding the commonalities between descriptions of data or knowledge is a foundational reasoning problem of Machine Learning, which amounts to computing a least general generalization (lgg) of such descriptions. We revisit this old problem in the popular conjunctive fragment of SPARQL, a.k.a. Basic Graph Pattern Queries (BGPQs). In particular, we define this problem in all its generality by considering general BGPQs, while the literature considers unary tree-shaped BGPQs only. Further, when ontological knowledge is available as RDF Schema constraints, we take advantage of it to devise much more pregnant lggs.