«

Is there any published system that includes sample source code, that
illustrates a good presentation / business / data layer partitioning of a
web based n-tier application?

The papers and books I have seen all deal with generalizations that are
mostly obvious and aren't very useful in committing something to code.
Everyone agrees that a well structured application should have presentation
layer, business layer, and data layer. The devil is always in details,
and no one publishes details. I want to see code for a large well
structured system that actually holds together and is easier to expand by
virtue of how it implements a layered multi-tier design.

The sample code I have seen, such as Microsoft's multi-tier sample
applications, appear to be completely amateurish efforts by college students
or people with no real commercial code experience. They are mostly
implemented in absolutely random ways that simply trivialize the value of
good architectural layering. I guess they are mainly meant as ways to run
Microsoft APIs.

I'm particularly interested in seeing:

- How authentication is handled, what kinds of cookies are created, and what
kinds of information is stored in each cookie. If authentication protocols
like Kerberos are being used, how are those integrated? Having code to
show just this piece alone would be highly desirable.

- How is the interface between the presentation layer that creates XML and
the business layer that handles business transactions handled, particularly
when the business layer is run on a separate computer? Getting the right
level of granularity in this interface seems hard. If you have all of the
data validation methods in your business layer, your presentation code is
making too many calls into the business layer, and that hurts performance if
you move that business layer to another machine.

--
Will