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RE: Reflective systems

From: Don Box <dbox@microsoft.com>
Date: Sun, 24 Feb 2002 02:01:38 -0800
Message-ID: <CFC4F26947496E4092489B2425614958042D3530@svc-msg-02.northamerica.corp.microsoft.com>
To: "Mark Baker" <distobj@acm.org>, "Rich Salz" <rsalz@zolera.com>
Cc: "Williams Stuart" <skw@hplb.hpl.hp.com>, <xml-dist-app@w3.org>
Not that the history of [O]RPC is worth rehashing, but...

Metadata describing COM interfaces was available through the registry
under HKEY_CLASSES_ROOT\TypeLib. Run OLEVIEW.EXE and look under the
Interfaces node in the tree control. I believe this even works under
UNIX/MVS builds of COM from Software AG.

CORBA made a big deal about interface repositories and I believe that
most vendors supported them much earlier than things like security or
transactions, given that the feature is fairly low-hanging fruit.

SOAP endpoints are described in WSDL/XSD for interop or proprietary
metadata (e.g., Java .class files, COM TLB files) for intra-vendor
solutions.

Since SOAP (and the protocol WG) are focused on interop, not proprietary
vendor solutions, one should be able to assume that any SOAP endpoint
that seeks to attain reach will expose its metadata via WSDL/XSD.

Also, don't confuse the presence/absence/format of metadata with the
ability to resolve an opaque type identifier to its metadata. The former
is addressed via WSDL/XSD. The later is addressed via the WSDL and XSD
"schemaLocation" attribute, which builds a NS-name/location pair for
resolving arbitrary namespace names to their underlying WSDL and/or XSD.

Cheers,
DB


> -----Original Message-----
> From: Mark Baker [mailto:distobj@acm.org]
> Sent: Monday, February 04, 2002 11:07 PM
> To: Rich Salz
> Cc: Williams Stuart; xml-dist-app@w3.org
> Subject: Reflective systems
> 
> >
> > > Absolutely true.  The wonderful thing about the Web is that this
is
> done
> > > *with* the Web.  It can describe itself.  RPC cannot.
> >
> > I disagree. Adding RDF to the web and saying it's reflexive seems no
> > different from adding DII to Corba, IDispatch to COM, etc.
> 
> I don't know about IDispatch, but IIRC, DII did not reify interfaces
as
> first class objects (i.e. they didn't get OIDs).
> 
> Also, while that's necessary, it's not sufficient.  What's also needed
> is a uniform means of resolving an identifer.  Neither CORBA nor COM
> has that, but the Web has GET.
> 
> MB
> --
> Mark Baker, Chief Science Officer, Planetfred, Inc.
> Ottawa, Ontario, CANADA.      mbaker@planetfred.com
> http://www.markbaker.ca   http://www.planetfred.com
Received on Sunday, 24 February 2002 05:03:00 GMT

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