something else to keep in mind, is the distinction between "IS-A" and "is-instance-of"

When designing a class hierarchy, the concepts of IS-A and HAS-A get thrown arround alot, but you have to always keep in mind that you are talking about "classes of things" -- not hte things themselves.

All i know about your data and your application is what you've posted in this thread, so maybe there's more going on then i understand, but it seems to me that "AcmeLtd" is an instance-of "Company", and "AcmeLtd IT" is an instance-of "Company::Division". Unless of course, you have some reason to instantiate many different instances of AcmeLtd ?

The nature of your data confuses me, so instead let's Imaging you are dealing with Animals. you've got the class "Animal" and hte subclasses Dog and Cat (a Dog IS-A Animal). now based on the nature of your data, do you want lots of instances of "Dog" representig a breed as an attribute, or do you want a seperate subclass for each breed, with each instance representing a physical dog with a name?

This...

# Dog ISA Animal

my $german_sheperd = new Dog(BIG, FURRY);
my $collie = new Dog(MEDIUM, SHORT_HAIRED);
my $poodle = new Dog(SMALL, GOOFY);
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...verses, this...

# Dog ISA Animal
# Dog::Poodle ISA Dog
# Dog::Collie ISA Dog

my $fluffy = new Dog::Poodle('fluffy');
my $spot = new Dog::Poodle('spot');
my $fido = new Dog::Collie('fido');
my $stray = new Dog();
[download]