The relations in Weyl groups can reflect to are reflected in Schubert varieties and then perverse the intersection homology sheaves, but this relation is not $\le$,for example,$l(s*u)=l(u)+1$,where \leq$. For example, when$l(s*u)=l(u)+1$, where$s$is a simple reflection,then reflection, then we have$C(s)C(u)=C(su)$,C(s)C(u)=C(su)$, where $C(?)$ is a left cell,what cell.