“…However, there are various spaces in mathematics, such as metric space, vector space, normed linear space, and inner product space. Among these spaces, the inner product space adds a "structure" [47], i.e., inner product, in which the angles and lengths of vectors are discussed and it can possess the properties of nonnegativity such as non-degeneracy, conjugate symmetry, first-variable linearity and secondvariable conjugate linearity. Therefore, in this paper, our objective is to explore samples in the inner product space and a framework that can potentially preserve the structure of the data space by integrating the structure of different elements in the higher-dimensional space into the lower-dimensional space via inner product operations.…”