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Re: [service-orientated-architecture] REST and SOA

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  • David Forslund
    ... Please define uniform Who is one to know of a text string is a method or a data element? Where am I to find out what is being sent over the wire?
    Message 1 of 42 , Dec 31, 2003
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      Mark Baker wrote:

      >On Mon, Dec 29, 2003 at 10:00:25AM -0700, David Forslund wrote:
      >
      >
      >>>I disagree, for reasons that may be clear from my response to Mark. I
      >>>think of REST as a very restrictive form of SOA in which services not
      >>>only have to be accessible remotely via message invocation, atomic
      >>>(i.e., they do one thing requested by the message and don't refer to
      >>>any implicit state from a previous operation), relatively
      >>>coarse-grained, etc. .... but also must be identified by URIs, be
      >>>conceived as the manipulation of the state of a resource, use a highly
      >>>constrained set of operations to perform that manipulation.
      >>>
      >>>
      >>>
      >>>
      >>I think this is so generic as to be not useful in the definition of a
      >>SOA. There actually
      >>is no real constraint in the REST interface, since anything can be sent
      >>over it.
      >>
      >>
      >
      >No, it cannot. I think REST is quite clear about this; that interface
      >semantics must be uniform. Anything not uniform, like "getStockQuote",
      >or "purchaseBook", is not RESTful.
      >
      >
      Please define "uniform" Who is one to know of a text string is a
      "method" or a data element?
      Where am I to find out what is being sent over the wire?

      Dave

      >Mark.
      >
      >
    • David Forslund
      ... Sure, but remember Netscape had an CORBA orb embedded in it for quite awhile which would have enabled people to use CORBA over the web . M$, however,
      Message 42 of 42 , Jan 4, 2004
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        Michael Champion wrote:
        On Jan 3, 2004, at 2:17 PM, David Forslund wrote:
        
        I'll let someone more familiar with CORBA respond to the assertion that 
        Prescod is "wrong" about it.
        
          
        I understand the "simplicity" of the REST approach, but I believe its 
        benefits are primarily illusory, largely because it
        is being used in rather simple transaction systems ("get me a catalog 
        of a certain type", e.g.).   It isn't clear how well
        it will work in a system with considerable more complexity.    
            
        I guess I agree, but would put it the other way around: If you have a 
        simple transaction system a la Amazon (or Google, which is even 
        simpler) leveraging the Web as REST does makes an awful lot of sense; 
        CORBA isn't really even an option for such things (after all, the whole 
        *point* is to make them universally accessible over the Internet), 
        Sure, but remember Netscape had an CORBA orb embedded in it for quite awhile which would have enabled
        people to use CORBA "over the web".  M$, however, refused to do the same in its browser.   Thus
        this option, freely available, was cut off from the general community.   The complexity of REST and CORBA
        in this scenario are pretty much the same.   A couple of calls pretty much provides what is needed.
        SOAP/WSDL appear to be overkill, and the customers have voted with 
        their feet against them.  If you have considerably more complexity, 
        well, the burden of proof is on the RESTifarians to show us real 
        working examples, IMHO. People building real, cross-platform, complex 
        enterprise transaction systems seem to be voting with their feet for 
        the Web services stuff in my experience, and apparently for CORBA in 
        David Forslund's.
        I agree that SOAP/WSDL are overkill (for this problem) and much more complicated than REST (or CORBA for that matter).
        I should say that my "vote" for CORBA is based on the fact that it works and works well in a very large
        number of complex commercial environments, not simply based on my experience with it.

        One issue that I've seen looking at REST, is that I can't get automatic code generation from a specification to
        the mapping between a REST interface to an OO implementation of the code behind it.   I can do this with CORBA
        and seem to be able to do this with Web Services (The MindElectric's GLUE comes to mind).  
        This may not matter for a simple application, but is very important for a complex application to reduce the amount
        of human-generated errors.  I would be interested in work that takes a REST approach and lets one build
        the basic structure of an application automatically (machine generated).   This requires some way of formally
        expressing the "interface" which can be translated by software.
        
        Sorry if this sounds wishy-washy (I know I irritate partisans of both 
        sides!), but as I put it in my Web Services Architecture summary at XML 
        2003, I think the choice of one approach or another to implementing 
        SOAs is a matter for case-by-case engineering tradeoff analysis, not 
        for general ideological debate.
        I think that is a good attitude, with the possible caveat that without adopted standards, we will continue
        to have chaos in distributed computing. 

        Thanks,

        Dave
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