Re: Web Services/SOA (was RE: XML 2004 weblog items?
On Tue, 30 Nov 2004 00:43:25 -0500, Mark Baker <distobj@a...> wrote: > On Mon, Nov 29, 2004 at 10:05:50PM -0500, Rich Salz wrote: > > I've never heard RPC described as SOA. I'd go back and challenge whoever > > told you that > > Many prominent folks have said that CORBA is SOA. For example; > > http://www4.gartner.com/pages/story.php.id.3586.s.8.jsp > http://www.microsoft-watch.com/article2/0,0,1220548,00.asp?kc=MWRSS02129TX1K0000535 > http://www.service-architecture.com/web-services/articles/service-oriented_architecture_soa_definition.html > http://groups.yahoo.com/group/service-orientated-architecture/message/1386 > http://www.capeclear.com/clear_thinking_soa.shtml Uhh, I don't think any of those prominent people (except for Mary Jo Foley, who is a *journalist* and can be forgiven for being fuzzy on the details ) were saying "CORBA is SOA". They are saying that the idea of "services computing" or "software as service" has been around for awhile and one *could* implement an SOA with CORBA (or DCOM, or Unix RPC I suppose) if one paid careful attention to the notion of services rather than objects or procedures. That doesn't mean that all CORBA or DCOM apps are examples of SOA. Nor are all SOAP applications SOAs ... any more than all C++ programs are object-oriented. For what it's worth, all these discussions beg the question of what a "service" is. I've taken a stab at this in http://www.cioupdate.com/trends/article.php/3434691 'In the real world, we use services all the time -- getting money from banks, ordering food from a restaurant, getting clothes dry cleaned, and so on. What makes these "services" is that we don't need to know anything about banking, cooking, cleaning, etc. in order to use them, we simply request them. ...In a nutshell, service orientation is an approach to designing systems in which each component knows only how to request and consume the services provided by other components, and little about their internal algorithms, data structures, stored data formats, query languages, etc. This is basically the value that web services add to service orientation. SOAP, WSDL, and the others are a set of specifications and technologies that describe in detail how to request software services using Web and XML tools.' That is, I'm basically arguing that one could build systems in which each component knows ONLY how to request and consume services from others using COM or CORBA or whatever (you would probably use very simple and generic methods with string-typed parameters to minimize what one component would have to know about the others, but it could be done). Obviously you can do this quite easily in the REST paradigm as well. XML, SOAP, WSDL, and WS-* offer more tools to explicitly describe the service interfaces and invocation procedures, but they can also lure one back the the Bad Old Days of needing to know too much detail about how a service does its job in order to use it.
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