Partial geometry

An incidence structure ${\displaystyle C=(P,L,I)}$ consists of points ${\displaystyle P}$, lines ${\displaystyle L}$, and flags ${\displaystyle I\subseteq P\times L}$ where a point ${\displaystyle p}$ is said to be incident with a line ${\displaystyle l}$ if ${\displaystyle (p,l)\in I}$. It is a () partial geometry if there are integers ${\displaystyle s,t,\alpha \geq 1}$ such that:

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