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Re: What are web services ?

  • To: Chiusano Joseph <chiusano_joseph@b...>
  • Subject: Re: What are web services ?
  • From: Razvan MIHAIU <mihaiu@m...>
  • Date: Tue, 31 May 2005 10:33:26 +0300
  • Cc: Paul Downey <paul.downey@w...>, Rex Brooks <rexb@s...>, xml-dev@l..., Michael Kay <mike@s...>
  • In-reply-to: <74B14CBC0FEB9D4EB16969F09FA51F4555AD25@M...>
  • References: <74B14CBC0FEB9D4EB16969F09FA51F4555AD25@M...>
  • User-agent: Mozilla Thunderbird 1.0 (Windows/20041206)

Re:  What are web services ?
>Although no single, authoritative definition exists for basic terms like "service" and "Web Service", here are some fundamental characteristics that some folks believe that anything described as a "Web Service" should possess:
>(1) Can interact with it through the WWW;
    Yes, this seems to be one of the goals. I saw in many article 
praising web services that they can pass thru standard proxies+firewalls 
because they are based on HTTP (like SOAP is)

>(2) Platform- and programming language-agnostic;
>(3) Interface & invocation requirements are well-described;
    I can some up with some well-described (in my opinion) protocol but 
that doesn't mean that it is going to be a web service. Microsoft can 
some up tomorrow with some new protocol called "M-SUPER-C" that will 
meet the above constrains but that does not mean that this is a web service.
    So point 3 is only valid toghether with point 9.

>(4) XML-encoded interaction mechanism;
    This is true according to W3C, but is this valid in the general 
sense ? Who says that a web service must be text-based and not binary ?

>(5) Payload most often is XML;
    "Most often" cannot be part of a definition.

>(6) Loose coupling between invoker and Web Service;
    You mean it must not have a state (like HTTP) ?

>(7) Performs a specific, well-defined function;
    !!!? I am really tired of such high level super-generic definitions. 
What entity in the computing world isn't supposed to be specific and 
well-defined ?

>(8) May invoke other Web Services;
    Remote invocation is not big deal. How about a self-describing 
feature (WSDL) ? Can a "service" be called a "web service" if it doesn't 
have this feature ? How about automatic discovery (UDDI) ? Is such a 
feature an integral part of a web service or is it just optional ?
    Of course WSDL and UDDI are just implementations. You can replace 
those with ASDF and YRRT or whatever.

>(9) Standards-based;
>(10) Has the ability to perform its functionality synchronously or asynchronously, as needed; (i.e. does not use synchronous interaction when asynchronous is best, and vice-versa);
    Can you please explain what you mean by this ?


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