Re: Interesting but sensitive topic to discuss (HELP: - OOP and CASE tools)

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Robert Martin says

"On the other hand,  if we need to add a new function to all the modems, then
in the first example, all we have to do is add a switch statement, but in
the second example, we must modify the abstract modem class and all its
derivatives.

This is an architectural choice; and it is based upon which kind of change
is more likely.  If it is more likely that new functions will be added to
existing modems, then the switch statement is probably the better choice.
If it is more likely that new kinds of modems will be added, then the class
structure is probably better.
"


Yes indeed, this is an important fundamental principle that does not seem
to be widely enough understood. It is useful to think of a matrix with
operations on the columns and types on the rows, then the issue of whether
to organize a program vertically or horizaonally with respect to this
particular subdomain is made on the basis of whether you expect to add
to rows or columns.

It is also appropriate to consider domains of expertise, does a typical
expertise extend over columns or rows of this matrix? If there is a clear
answer to this question, which is sometimes the case, then that may be
another consideration in deciding whether to organize horizontally or
vertically.