Maybe these are very basic questions or I have neglected something, but I'm a bit confused by the two requirements in the definition of "enriched category", i.e. \\( I\leq\mathcal{X}(x,x) \\) and \\( \mathcal{X}(x,y)\otimes\mathcal{X}(y,z)\leq\mathcal{X}(x,z) \\). First, why does the definition use "≤" instead of "=" or "≥"? Second, why does the relationship between \\( \mathcal{X}(x,x) \\) and \\( I \\) matter (such that it must be written into the definition)?