Re: How could RDDL be distributed ?

[Michael Mealling <michael@bailey.dscga.com>]

On Tue, Jan 16, 2001 at 04:01:11PM +0000, Miles Sabin wrote:
> Michael Mealling wrote,
> > Miles Sabin wrote,
> > > To do the job you'd need some mechanism for ensuring that all
> > > the DTDs were cached locally before pulling out the wire. 
> > > It'd be nice if that local caching mechanism got along well 
> > > with a mechanism for connected distribution and replication.
> >
> > That's one way but I don't think it solves the whole of the 
> > problem. Your still associated resources that are what I call 
> > authoritative. I think you want a solution that allows you to 
> > associate locally scoped resources as well.
> 
> Actually I think it's simply two different problems which might
> have related solutions,
> 
> 1. Allow for local overriding of authoritative resources.

IMHO that's the c15n problem space...

> 2. Allow for distribution and replication of authoritative
>    resources.

That's the URI Resolution problem space. The one part that 
isn't there is the actual distribution and replication part.
Since I don't think we'd be doing really complicated
stuff some of the existing rsync-ish solutions would work fine.
The one piece that isn't there is an API for notifying the
URI resoution services that a replication has occured.
I think you'd also need some metering so that you can
do some pro-active replication to hot spots but that
also has some standard solutions.

> (2) is the problem I'm worrying about ... my starting point
> being a worry about the hosts for popular DTDs/Schemas becoming
> a single point of failure.

Same here. The CNRP stuff I published had to include a 
non-existent URI in the examples so that people wouldn't
be using that URI due to lazy programmers. The URN/URI
resolution stuff was built specifically for this purpose....

> Interestingly the two problems are dissimilar in a very
> important way. (1) explictly wants to allow for substitution/
> overriding (that's it's whole point). (2), OTOH, almost certainly 
> wants to verifiably forbid substitution/overriding (or at least 
> make any such modification visible to ultimate recipients). That
> seems to imply a need for signatures to be accomodated by any
> such protocol.

Exactly! The whole concept behind the c15n stuff was that
this was URI Resolution that explicitly wasn't authoritative
since it was being used to provide a view of the world that
was client centric. The URi resolution stuff (and specifically
RESCAP) does have the ability to sign various bits to ensure
the authoritative chain of resolution....

-MM

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