On schematic orthogonal arrays of high strength

Schematic orthogonal arrays are closely related to association schemes. And which orthogonal arrays are schematic orthogonal arrays and how to classify them is an open problem proposed by Hedayat et al. (1999). By using the Hamming distances, this paper presents some general methods for constructing schematic symmetric and mixed orthogonal arrays of high strength. As applications of these methods, we construct association schemes and many new schematic orthogonal arrays including several infinite classes of such arrays. Some examples are provided to illustrate the construction methods. The paper gives the partial solution of the problem by Hedayat et al. (1999) for symmetric and mixed orthogonal arrays of high strength.