[FoRK] Open Link: Objects+piping (and better)+real loose coupling

Stephen D. Williams sdw
Mon Oct 3 20:05:04 PDT 2005

Gavin Thomas Nicol wrote:

> On Oct 3, 2005, at 4:38 PM, Stephen D. Williams wrote:
>> We've argued out the *XML thing to death.  I believe that it's the  
>> semantics and idioms of XML that are important, not the encoding as  
>> primacy.
> That's the problem though... XML is a syntax, and nothing more.  
> People keep *claiming* it's more, but it's not.

I saw many years of AX (ante-XML) and there have been a few PX (post-XML 
(well, really during-XML)).  There was a phase change, / paradigm shift 
where the level of sophistication of thinking and concentration on data, 
structure, validation, typing, evolution, etc. became far more 
sophisticated.  This happened in and around XML and is inseparable from 
it to some extent because of that.  The same thing happened with Java 
and many related libraries and frameworks in many respects.  In both 
cases, many of the methods could have been used before in C/C++, CORBA, 
DCE RPC, etc. but didn't because existing 'best practices' couldn't 
change enough.

>> Anything that substantially is in the mold of XML should be related  
>> to XML.
> Disagree.
>> I think that everthing should be roundtrippable through XML 1.x but  
>> not limited by it.
> Agree.
>> I've decided that three modes need to exist: text-only self- 
>> described (just like text XML), typed data self-described (XML-like  
>> with typed binary payloads, int, IEEE, etc.), and meta-structured  
>> transformation into various levels of non-self-described  
>> representation where the structural and typed description has been  
>> externalized into an interpretable metadata object.  All three are  
>> needed.
> They're all different shades of the same problem, and yes, I tend to  
> agree that depending on the application one of the three could be  
> more useful than just one for all applications. The latter two, IMHO  
> generally (at least at an API level) tend to look similar.

I had something of an epiphany in the XBC working group that helpd unify 
styles of data representation on a gradual scale from totally 
self-describing / self-framing / explicit structured (XML) to no holds 
barred bit packing (hand coding, ASN.1 encodings like PER).  This scale 
illustrates the level of "externalization" of structure and typing in 
all senses.  In the old days, like Sun ONC RPC, much of the structure 
and typing knowledge was externalized to and represented by C code.  For 
ASN.1, it's represented as ASN.1 syntax by typically compiled into code 
stubs.  XML has very little externalization, although you could count a 
schema and higher levels of data understanding.

>> I don't believe in fundamental strucuture typing.
> I think it depends on the application, but in general, for *data* I  
> prefer "type by assertion" rather than "intrinsic typing". Here of  
> course, "data" depends on what you're looking at, but in general, the  
> tighter-bound you get, the more likely I would be to use strong  
> typing (i.e. write objects rather than generic manipulators) because  
> it would tend to expose the details of the data more clearly.
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swilliams at hpti.com http://www.hpti.com Per: sdw at lig.net http://sdw.st
Stephen D. Williams 703-724-0118W 703-995-0407Fax 20147-4622 AIM: sdw

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