[EMAIL PROTECTED] wrote:
> >Gregg Wonderly:
>
> What web service do is completely isolate the application from network based
> computing. You get to reimplement all of the facilities of the network
> protocols
> because you can only send data. This is where web services break down.
>
> Good point.
>
> Just to check I have it right: Another way to say this is "Protocol
> independence
> is an illusion" - yes?
You are always dependent on the protocol. The features and the limitations are
very real. XML is part of the protocol and presents a limitation since it is
"data". How would you write a portable application using web services that
would provide access to an FTP server? The answer is that web services can not
be the solution. You'd write a program (using an available FTP client library)
that provided a programatic interface to the features that you need. Then you'd
export a service that was accessible via appropriate interfaces. If you wrote
the service in Java, you could chose to export it as a Jini service using
multiple endpoints, which might include a web services endpoint. If you write
it in another language/platform, you'd be able to export it using the available
implentation(s) there.
If you choose Jini, then, you can provide an endpoint with a smartproxy
implementation. The smartproxy might actually implement the FTP interactions
on
the client instead of locally. Why would this be interesting? Well, what if
the data is close to the user, and not close to the "server" that hosts the
service definition?
Instead of having a "server" collect the data, across the network (what if the
user's network is on a satellite link where bandwidth costs real money?), and
then send it back across the same network to the user, the user can get it
locally, with no remote network transactions.
This is just one example of where choices are helpful. The user might be in an
isolated network where there is no place for a local "server" to exist to host
the service.
And, this is exactly the type of service that I develop on a regular basis.
Gregg Wonderly
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