Re: What makes Java so special?

Hi, Dean

At 07:24 PM 11/23/97 -0500, you wrote:
>Chris,
>
>In a message dated 97-11-22 17:25:12 EST, you write:
>
><<snip>>
>> So, your application issues a request to an object broker which translates
>>  that request off to the target system. The use of object brokers, as you
>>  point out, insulate your client machine from it's target. But that doesn't
>>  mean that your client application is platform independant. It could be
>>  compiled C code on a CPM machine. So, while the client code can't move, it
>>  doesn't care what kind of machine or application is issuing a response
>since
>>  it is using an object model standard for it's requests. 
>
>Oh, I didn't mean to imply that the client object should be
>platform-specific.  I just thought that your "broker", for example, would
>call an ODBC server as a "generic" database server _BUT_ could _also_ call an
>APPC connect such as ESS/400 in an instance where the AS/400 was the target
>to improve performance.  Wrong?

In a way, everybody's "right". To a certain extent, it all depends. The
design may rely on programmer skills, projected platforms in use, whether
anything will change soon, time, small shop, software house, etc.—all the
things y'all know.

I find a "logical" 3-tier concept useful, and I think it is something like
Chris was talking about in a recent post—something that's been possible for
years, if a designer chose to implement it. It's something like this:

  Presentation             Service                 Data
  +----------+           +----------+           +----------+
  :          :           :          :           :          :
  :          :           :          :           :          :
  :          :     ______:          :     ______:          :
  :          :_____\     :          :_____\     :          :
  :          :           :          :           :          :
  :          :           :          :           :          :
  :          :           :          :           :          :
  +----------+           +----------+           +----------+

Now, where these layers reside is not too critical, at one level. They
could all be on the same machine, using MS Access or dBase or whatever.
Various combinations of these one the different boxes result in the 5 or so
models that IBM has propagated for C/S—and none of this is anything but
good old distributed computing with a new name, as fas as I can see.

In the end, these concepts need to be implemented, and that's a design
issue—where do you put what? And that depends on a lot of things. And
portability may come in here somewhere. The "write once, run anywhere"
piece of Java seems to apply best to the "Presentation" part, getting at
the data via (perhaps) an optimized "Service" layer.

Just some very sketchy thoughts—

Vernon Hamberg
Systems Software Programmer
Old Republic National Title Insurance Company
400 Second Avenue South
Minneapolis, MN 55401
(612) 371-1111 x480


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