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   Re: [xml-dev] What are web services ?

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Paul Downey wrote:

> On 29 May 2005, at 17:42, Razvan MIHAIU wrote:
>>>              Were can I find a good definition of this ?
> my definition is it's a service made available using Web based
> technologies targeted at computer, as opposed to human, agents.
    It seems that you are right (according to W3C):

"The World Wide Web is more and more used for application to application 
communication. The programmatic interfaces made available are referred 
to as Web services."

 ... "applications to application". What this definition implies is that 
the term is very generic. Everything can be a web service:

1. a cgi
2. an ejb
3. a php/perl script


the only restriction is that the above entity must communicate with a 
computer and not a human.

    However there must be other restrictions for web services. After 
reading the other definitions I came up with the following list:

1. interoperable between OSes (a message written on one OS should be 
easily readable on another); this seems to imply the use of XML; what 
other technology can achieve this ?
2. it must be an open standard (issued by Oasis or W3C); this 
restriction should rule out any "cgi, ejb, perl/php script" as a web 
service; you could have a cgi acting as a web service but only if it 
works according to a certain open protocol (this leads us to the next 
3. it must have an open interface (e.g. it must work according to a 
certain protocol); as I read in another reply there are at least 3 
protocols to match this criteria: SOAP, REST, XML-RPC

    Any other restrictions ?

> Some attempts at definitions:
> http://www.w3.org/2002/ws/
> http://en.wikipedia.org/wiki/Web_services
> http://ws-i.org/about/Default.aspx
> http://msdn.microsoft.com/webservices/
> Google until your blue in the face ..
>>> A web service must be based on SOAP in order to belong in this 
>>> category ? A web service must use XML for transferring data (like 
>>> SOAP) ?
> Web services are synonymous with SOAP, WSDL and UDDI in many
> peoples' eyes, though they've taken so long to arrive
> that the marketeers are busy re-branding it 'SOA', I
> guess SOAP is now Service Oriented Architecture Protocol :-)
>>> Can we have web services without WSDL and UDDI ?
> Sure, why ever not? It's the service that's important, not
> how you elect to describe, catalogue or sell them.

    Doesn't a web service imply the fact that it can be found in a 
standard way ? Or this is just an add-on to the web service definition 
that may or may not be fulfilled.

    The truth is I have yet to see a programmer that answers this 
question with a big smile. Why is the question difficult ? Perhaps 
because behind web services there are so many technologies or perhaps 
because the term has not finished evolving yet.


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