FW: For Tuesday (More about top-down XRD stuff)

["Steven Churchill" <steven.churchill@xdi.org>]

FYI:

 

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From: Steven Churchill [mailto:steven.churchill@ootao.com]
Sent: Saturday, February 07, 2009 7:24 PM
To: 'John Bradley'
Subject: For Tuesday

 

John,

 

Here’s what I have in mind for Tuesday:

 

The problem is that the  XRI TC is still trying to define the entity discriptor format (the new XRD) outside the context of its overall entity discovery framework.

 

As I said in my last email to the TC (a few months ago), an entity discovery frameork has:

 

1.       Entity space
Entities have:
a) “Generic” characteristics. These are the characteristics that are obtained using the service access rules. In other words, an entity’s generic characteristics can be anything we want because we formalize how to get them via service type and URI. (The entitys’ generic characteristics are extensible.) Good design!

b) Structural characteristics. Hierarchical children; poyarchical references, and so forth.

 

2.       Discovery function

Input: identifier (and perhaps plus other stuff)

Output: entity descriptor (and perhaps other stuff)

 

In XRI this devined by “XRI resolution”

3.       Identitfier fomat

In XRI, this is, well, an XRI.

4.       Entity Descriptor format

Returned by the discovery function and used to access structural and/or generic characteristics (via indirection.)

 

John, as I mentioned above, for the new XRD, the TC is trying to define (4) without properly considering 1-3. For example, from a purely abstract standpoint, what should 4 contain? It should contain:

 

·         The “generic characteristics” -- or more specifically, how to get to them using the service access rules.

·         Structural characteristics. In XRI, the direct hierarchical children can be obtained indirectly via an authority service. [[N.B: Note in XRI how it’s silly to bury this structural characteristic inside the service access stuff. Gratuitous overloading again.]]
The polyarchical references (Refs) and disguinshable identifier (CID) are both structural characteristics.

·         Bookkeeping stuff needed by the discovery function. In XRI, this includes <Query>,  sigs, nested XRDS for auditing, etc.

That’s pretty much it.

 

So let’s talk Tuesday about the new XRD as an entity descriptor – but from the context of it’s items (1) and (2) above (that is, from the context of it’s entity discovery framework.)

 

The bottom line is that I don’t think anyone really understands either the entity space or the discovery function, and without those, the TC really should not try to define the descriptor format.

 

Gracias,

 

~ Steve