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

David Chizmadia vze2729k at verizon.net
Mon Jan 20 23:10:30 UTC 2003

On Monday, January 20, 2003 5:19 PM, Mark S. Miller wrote: 
> At 12:44 PM 1/20/2003 Monday, Tyler Close wrote:
> >No, but doc-code is just an alternate representation of 
> >the XML. XML is a standard. There are standards for 
> >specifying the structure of an XML document. XML also 
> >seems to be a more popular standard than CORBA. If you're 
> >looking to jump on a bandwagon, XML seems like the better 
> >horse to bet on.
> I endorse this perspective. In the modern world, for a 
> system to be widely adopted, code must use curly braces 
> and data must use angle brackets. Just as E concedes on 
> the curly bracket front (ie, the C-tradition syntax issue) 
> in a minimally offensive way, and without conceding on the 
> issues that matter; it looks to be me that WOS does likewise 
> on the angle bracket front (ie, the XML compatibility issue).

As I'll discuss below, OMG has recognized this as well, with
exactly the same misgivings as you! I think that the OMG
approach to textualizing CDR in XML addresses your concerns.

> To reiterate, what I need for the next CapTP is a readable 
> textual syntax that can honestly claim to be XML compatible 
> without paying the complexity costs that normally come with 
> such a claim, together with an efficient binary syntax which 
> encodes exactly the same meaning. WOS looks like it meets 
> these goals well. I've heard the OMG has defined an XML syntax 
> but I haven't seen it. David, do you have a URL? For use in 
> CapTP, any comparison of CDR to WOS must compare both the 
> binary syntaxes and the XML syntaxes.

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:

> 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.


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