On ID "sameness"

[Ray Plante]

Hey Arnold,

> I think I'm seeing the light.
> The solution may lie in imposing a logical mapping between objects,
> name spaces, and IDs, leaving that mapping up to the issuer of the
> object.  

Cool.  I think we're on the same page there.

> As far as I am concerned we can equate name spaces and IDs.
> But it does require a fully hierarchical object space.
> 
> I admit that this is more of a use case than a requirements
> discussion.  But I think it clarifies a number of things.

(Hey, use cases were called for as well!)

I agree.  I, too, concluded that a hierarchical space would be helpful.  
(I've been thinking about a form based on the URI standard; however, the 
functionality is identical to your examples.  No matter--just an 
implementation detail.)

> As far into those remainders as they are identical there
> is sameness, but you would probably have to look at the metadata to
> determine the degree of sameness.  For instance, CXO:2000 in
> NASA:HEASARC:CXO:2000 and SAO:CDA:CXO:2000 indicate that we are
> pointing to the same observation

I think this is a repeat of what you just said, but I would that one would 
have to look at the metadata for NASA:HEASARC:CXO:2000 to know that it 
refers to the same observation as SAO:CDA:CXO:2000 as there is no a priori 
way of knowing that those common parts are intentional or accidental.  

> As I said at the beginning, I would suggest that:
> 1. We assume/require a one-to-one logical mapping between objects,
> name spaces, and IDs
> 2. The object (ns, ID) space be strictly hierarchical
> 3. The issuer of objects in a given name space be responsible for
> issuing authoritative IDs

I agree with all three of these.  Strictly speaking, I see 2. as a 
technical choice that should be motivated by some required functionality.  
The functionality you describe (I think) is the ability to determine in 
one object logically contains another.  Personally, I motivate a hierarchy 
by the need to be able to access descriptions of objects from an ID.  It 
is likely that a description may not be explicitly available for all 
objects that are assigned an ID; however, if we require that a registered 
description exist for at least the top-level containing object, then you
can work your way up the hierarchy until you discover something about the 
object.  

Thanks for the use cases!

cheers,
Ray