URI comparison for resource identification
A resource owner SHOULD assign a URI to each resource that others will expect to refer to.
Refer to includes use as a name and dereference.
Use string compare when used as a name. If they are the same, they refer to the same resource. If they aren't, you don't know (Web architecture does not constrain a Web resource to be identified by a single URI.) This is the same algorithm as Namespaces in XML. It avoids false positives and risks some false negatives.
Resource owners should not create arbitrarily different URIs for the same resource.
Resource retrieval (eg cacheing) will use different equality operators for URIs (default ports, domain names case insensitive, etc) to reduce false negatives.