Definition:Open Refinement
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Definition
Let $T = \struct {X, \tau}$ be a topological space.
Let $\UU$ and $\VV$ be covers of $X$.
Then $\VV$ is an open refinement of $\UU$ if and only if:
- $(1): \quad \forall V \in \VV: \exists U \in \UU: V \subseteq U$
- $(2): \quad \VV \subseteq \tau$
That is:
- $(1): \quad \VV$ is a refinement of $\UU$
- $(2): \quad$ All elements of $\VV$ are open in $T$