"wbsurf...@yahoo.com" <wbsurf...@gmail.com> wrote:

"Martin Mandl - m2m tech support"

Your first question was about sharing databases. Martin's answer addressed
that. Your second question seems to be about sharing logic (modules), but I am
not sure I understood you completely.

Of course it's possible, in fact common to share code libraries among multiple
languages; no need even to limit it to two. This predates Java - CORBA doesn't
give a rat's a.s what languages are involved. Service-oriented architectures
(SOAs) have been around since before XML, too, but now with SOAP-based web
services it's almost trivial to share code, or more descriptively, services
without regard to the programming languages involved. I've worked on
SOAP-based systems that interoperated between .Net/C# (VB) and JEE platforms.

The issue of sensitivity to "slight" or even major data-model changes also
transcends the implementation language. It's a matter of architecture.

In one common approach, the data-access component presents an object model to
the rest of the application, while persisting data to a relational store. The
object and relational models depend on the requirements analysis and logical
design of the system. The choice of Java, C#, COBOL or machine language for
the implementation should affect only performance characteristics: man-hours
and calendar time to deployment, speed of data access and the like.

Whichever language you choose, if the data model changes you likely will have
to change application characteristics, too. How easy that is depends on how
the components interact, not the implementation language. In well-designed
applications one might change only a few XML deployment descriptors for most
alterations. SOA as an approach is popular partly because it adapts well to
design changes.

-- Lew