Orbital schemes of \(B_3(q)\) acting on 2-dimensional totally isotropic subspaces (Q1266359)

The authors determine the intersection numbers of the association scheme (with 5 classes) on the set of (totally isotropic) lines on a non-singular quadric in \(\text{PG} (6,q)\). They also prove that merging classes does not yield an association scheme. Actually these results can also be obtained by using classical formulas that can be found for instance in \textit{J. W. P. Hirschfeld} and \textit{J. A. Thas} [General Galois geometries (1991; Zbl 0789.51001)].