Using URLs vs. URN OIDs: best practice?

[shibboleth655 at lewenberg.com]

Our IdP releases several institution-specific attributes with names that 
are not URI's, e.g., "workAddress" and "departmentalAffiliation".

We are working on changing this. Several of these attributes come from 
our LDAP and, since we have our own LDAP OID namespace, have globally 
unique OIDs.

We are considering two options for the new names:

1. Use our OID, as in "urn:oid:1.x.x.x.x.x.x"

2. Use a globally unique URL, such as 
"https://attribute.our.domain.net/saml/workAddress".

The second format has a couple of obvious examples: it is easier to see 
from the name what the attribute is and, as the name is a URL, we can 
set it up so that going to that URL displays the documentation on that 
attribute.

In fact, Internet2 encourages this (see 
https://www.internet2.edu/products-services/trust-identity/mace-registries/#service-faq 
)

Before embarking on this large change, I wanted to know if there are any 
advantages to using the "urn:oid" over the URL? Remember, that right now 
for several of our attributes we are using _neither_.

Thanks you, Adam Lewenberg