Multiprojective Seshadri stratifications and Young-tableaux

We provide an algebraic-geometrical interpretation of the classical semistandard Young-tableaux via the notion of Seshadri stratifications. The columns appearing in such a tableau correspond to vanishing multiplicities of certain rational functions on Schubert varieties. To build a framework for this correspondence we generalize Seshadri stratifications to multiprojective varieties, which forms the largest part of this article.