Major Description
The NamespaceRegistryImpl.getURI and getPrefix are called a lot, for example by NamePathMapperImpl.getOakName.
The method doesn't do any caching, which is a problem because it has to read it each time from the repository. Even if it would do caching, it wouldn't help because it the method WorkspaceImpl.getNamespaceRegistry creates a new NamespaceRegistryImpl each time it is called. To allow caching of known mappings, the instance needs to be cached as well.