1. In a namespace federation infrastructure, a method for processing a namespace lookup request, the method comprising: a namespace manager receiving a namespace lookup request that includes a namespace identifier identifying a path to a particular namespace branch of a namespace tree, the particular namespace branch being one branch in a plurality of hierarchically-arranged namespace branches of the namespace tree, each namespace branch corresponding to a different resource within a hierarchical arrangement of a plurality of resources, each namespace branch being registered to a different corresponding provider of a plurality of providers; the namespace manager choosing a proximity metric for limiting a routing scope of the namespace lookup request to only providers that are within a defined proximity from the namespace manager; the namespace manager determining a namespace lookup request type of the namespace lookup request, including determining that the namespace lookup request type is either (i) a generic request type or (ii) a targeted request type; and based on determining the namespace lookup request type of the namespace lookup request, and based on the proximity metric, the namespace manager forwarding the namespace lookup request using either generic routing or targeted routing, including: when the namespace lookup request type is the generic request type, the namespace manager forwarding the namespace lookup request using generic routing to (i) a provider that is registered to the particular namespace branch and that is specified in the identified path, (ii) one or more first providers that are registered to a namespace branch hierarchically above the particular namespace branch in the identified path to the namespace branch, and (iii) one or more second providers that are registered to a namespace branch that is hierarchically below the identified namespace branch; or when the namespace lookup request type is the targeted request type, the namespace manager forwarding the namespace lookup request using targeted routing to the provider that is registered to the particular namespace branch and that is specified in the identified path, wherein when forwarding the namespace lookup request, the namespace lookup request is forwarded only to the providers that are within the defined proximity from the namespace manager.