This is a software design question - ILE related

The example I'll use is hypothetical.  But, the question applies to a real
application I'm working on.

With ILE you're encouraged to encapsulate code according to subject into
reusable components.

With that preface, here's the hypothetical:

An ERP application has separate "service programs" for encapsulating code
related to "employees", "vendors", "customers", "sales leads", etc.  One
thing common to each module is "person" related data (i.e.. name and
address).  Each separate module needs to use a "zip code" file to look-up
the "city" associated with a zip code.

For modularity, one idea is to create a single service program that opens
the zip code file, and exports a function that returns the city for any
given zip.  All other modules in the application can simply "bind" to, and
use that function.  It saves little code by not including the record
retrieval code in each module.

To summarize, the application might have the following structure:


ERP
 |-----"EMPLOYEE MODULE" ------"CITY LOOKUP MODULE"
 |-----"VENDOR MODULE" --------"CITY LOOKUP MODULE"
 |-----"CUSTOMER MODULE" ------"CITY LOOKUP MODULE"
 |-----"SALES LEADS MODULE" ---"CITY LOOKUP MODULE"
 |-----"OTHER MODULES" --------"CITY LOOKUP MODULE"


Another idea is to turn the "CITY LOOKUP" module into a server rather than a
service program/sub-procedure.  A set of data queues could be used to send a
zip code - receive a city (in the context of a single request).  The
application might have the following structure:

ERP
 |-----"EMPLOYEE MODULE" ------
 |-----"VENDOR MODULE" --------
 |-----"CUSTOMER MODULE" ------
 |-----"SALES LEADS MODULE" ---
 |-----"OTHER MODULES" --------


       ---Data Queue Set---


        CITY LOOKUP SERVER


The ERP application may have thousands of concurrent users.  Which design
approach would you take, and why?  Or, would you do something else?


Thanks.


Nathan M. Andelin


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