Ali wrote:
>> While there would be fairly powerful processing to an extent, it's
>> still a resource-constrained environment, running on an RTOS (I think
>> VxWorks). In particular they are concerned about dynamic memory (don't
>> like it).

Remember, XML is just a syntax. How you represent the data after it has 
been parsed is a separate question. Depending on what you're doing, you 
may not need an in-memory representation at all; you may be able to feed 
the information parsed out of the XML directly into your application's 
data structures (sometimes referred to as "data binding"). The simplest 
way to start in that direction would be to use an efficient SAX (or 
SAX-like) parser.

> WSDL/XML/SOAP are just common ways of information exchange for systems
> with ample processing and hell memory.

Disagree, somewhat. As noted above, memory consumption depends on the 
data representation you choose much more than the syntax you use to 
exchange it. And XML parses and serializes pretty rapidly, given decent 
code -- rapidly enough that the various attempts at "binary XML" have 
generally proven that the gains available are fairly minimal. Yes, if 
you have control over both ends of the wire you can certainly create a 
more compact/efficient representation, and XML does carry some features 
you may not need and pay some overhead for them (eg Unicode support)... 
but don't dismiss it out of hand, especially if you intend to expose 
this wire protocol to others.

The overhead drops further if you're willing to constrain yourself to a 
specific set of messages. IBM's demonstrated that tremendous 
improvements in parsing performance are available if you know in advance 
what schema the document will belong to, with further gains if you're 
willing to insist that the doc have been validated on the sender's end 
(letting the parser rapidly skip over "boilerplate" and jump directly to 
the document's content).


There are certainly folks putting web services in low-powered embedded 
boxes -- most cheap routers these days support a simple web GUI, for 
example. "If it happens, it must be possible."

-- 
() ASCII Ribbon Campaign  | Joe Kesselman
/\ Stamp out HTML e-mail! | System architexture and kinetic poetry