[e-lang] [RFP] cross-language object serialization (E <---> Squeak-E)

Tyler Close tyler at waterken.com
Tue Jan 21 00:15:01 UTC 2003

On Monday 20 January 2003 19:10, David Chizmadia wrote:
> I've only just started studying it, but what OMG has done is
> define XML DTDs for expressing CDR constructs in XML documents.
> In effect, this provides a textual representation of the binary
> CDR format.
> The specification can be found at URL:
> ftp://ftp.omg.org/pub/docs/formal/02-11-10.pdf

Are you sure this is the right specification?

The "XML/Valuetype Mapping Specification" defines a mapping from
XML to IDL, not from IDL to XML. This means they have specified a
way of representing a DOM tree in IDL. The purpose of the mapping
is to have a way of manipulating DOM trees in IDL.  The resultant
model is a combination of the complexity of the DOM *and* IDL.

What we're looking for is a mapping from IDL to XML. The spec says
this is covered by the MOF and XMI, but I haven't been able to
find it yet. Those two are awfully large.

>> Technically, saying "CDR compatible" means something, whereas
>> saying "XML compatible" is mostly vacuous[*]. But marketing-
>> wise, the situation is reversed. The world has gotten stupid.
>> [*] Saying "Compatible with XML DTD Foo" would be non-vacuous,
>> but there is no standard XML DTD I'm aware of that would be
>> suitable for this purpose.
> The neat thing about the XML/ValueType specification is that it
> effectively allows you to say "Compatible with CDR binary or XML
> encodings". This lets one attain the technical value of CDR *and*
> the marketing value of XML.

I am going to make a bold claim, which may be wrong. Hopefully
doing this will help us extract information. I claim that the only
technical advantage of CDR over doc-code is that the type names
used in the CDR already have widely accepted meaning; whereas the
type names in WOS are new. (The type names belong to WOS because
doc-code has no hard-coded type names, unlike CDR.)

Note that I am not saying that doc-code has no technical
advantages over CDR. I believe it does.

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