Mark Woyna wrote:
> Gerald Brose <gerald.brose@x...> wrote in message news:<2i5gvaFhvjq7U1@u...>...
> 
>>For loosely coupled application-to-application communication
>>that cannot rely on a homogeneous middleware layer such as
>>CORBA and may need to be rearranged to integrate more systems
>>every other month, you will be better off with Web Services.
> 
> 
> What is Web Services if not the next attempt at a homogeneous
> middleware layer???

It is a lot "less homogenous" than CORBA.

> CORBA was to be *the* standard for heterogeneous distributed
> computing. Since one important company, read: Microsoft, did not buy
> off on the vision of a heterogeneous computing environment, the world
> was left with two major platforms: CORBA and COM/DCOM/COM+/etc, and a
> collection of proprietary MOM products. The fear that Sun would
> succeed in using Java to provide a uniform distributed platform led
> Microsoft to push for a cross-language, cross-platform solution, i.e.
> SOAP and Web Services. This does not change the fact that there was a
> standard open model for distributed computing.

Sure, that's the history, but this is ignoring the actual technical
differences between CORBA and the SOA/Web Services which account
for the different sweet spots. But first let me spell it out again:
neither CORBA nor SOA/Web Services are "better" per se, they have their
strong points in different usage areas. You seem to be implying that
CORBA would have been the universal silver bullet for all your distributed
scenarios, which it just not the case.

The two models differ in important aspects. CORBA's, with the notion
of objects in the OO sense, is much richer; and more of the interaction
semantics is spelled out in the spec. While this is nice if you are
in an OO language, it entails many assumptions for the interaction
between clients and servers. It also means that you need to have a
complete ORB marshallin engine for even simple things, i.e., you cannot
simply run a PERL script to fire a message. (I would like to point out
Steve Vinoski's "Middleware dark matter" article to all those believing
that CORBA is the only true middleware around.) For SOAP, all you need
is an XML parser. (I know, they are complex too, but they are much
more available and easier to integrate than isolated GIOP/CDR mar-
shalling engines)

CORBA also spends a lot of space on specifying APIs for portability
purposes (e.g. POA, PIs), which is completely out of scope for SOA/Web
Services. You can use portable APIs (e.g. JAX-RPC) but you don't
have to. Web Services as a middleware are more modular, if you like,
and it also suffices if the two parties that actually interact know
what it means. It's enough to pick those pieces off the standards
that are required for the task at hand.

To cut this long story short: in B2B it is a lot easier to
retrofit a thin Web Services layer onto applications to connect
existing stuff than to agree on CORBA and on IDL interfaces
and then wrap things.

>>XML messages are especially suited for document-style inter-
>>actions, and the performance hit is tolerable in many of
>>these applications. People also tend to believe that the
>>firewall-friendliness of HTTP is a good thing...
> 
> 
> Yes, believe. Like kids believe in Santa Claus. They'll believe until
> some of their customers private data goes walking out port 80, and
> then we'll see those ports closing up.

Well, the "..." was meant to signify that that is of course
naive for any production environment. However, it comes in handy
for larger-scale inhouse scenarios (say, for testing) where CORBA
requires you to use an IIOP proxy, like Xtradyne's I-DBC, for
firewall traversal.

For any real-world, extranet settings any "port 80" is closed, so
you need a Web Services Security Gateway (like Xtradynes WS-DBC),
too. However, the Web Services approach to security (while necessarily
reinventing some parts of the wheel) is a lot more modular and
promising than CORBASEC ever was.

Cheers, Gerald
-- 
Gerald Brose, PhD                       mailto:brose@x...
Xtradyne Technologies                     http://www.xtradyne.com
Schoenhauser Allee 6-7,                  Phone: +49-30-440 306-27
D-10119 Berlin, Germany                  Fax  : +49-30-440 306-78