ora-0022

1.10 Weak equivalence and localization

Strict isomorphism is often too rigid for learned representations. Two models may encode the same observable decisions through different coordinates, factorizations, or resolutions.

Definition 1.22 Relative category

A relative category is a pair \((\mathcal D,W)\), where \(\mathcal D\) is a category and \(W\) is a declared class of weak equivalences containing all identities.

Localization formally makes every map in \(W\) invertible:

\[ \mathcal D\longrightarrow \mathcal D[W^{-1}]. \]

The localization is best regarded as an \(\infty \)-category when the paths and higher witnesses relating weakly equivalent presentations matter.

Design principle

Weak equivalence is semantic data. UODL must state which observables a weak equivalence preserves. Choosing a familiar model structure does not by itself justify identifying two decision systems.