Tits geometry on ideal boundaries of Busemann non-positively curved   space
  Let $X$ be a non-compact proper Busemann space. We introduce a collection of binary relations on its ideal boundaries generalizing comparison of Tits metric with two key values $\pi$ and $\pi/2$. This allows to use properties of Tits metric known for CAT(0)-space without metric itself. 
P.D. Andreev