>> "Extending"
> > a document type can break applications which is more or less what
> > happens in binary formats too!
>
> Type inheritance in XML Schema can provide extensibility
> benefits to the
> author of the original schema.
The gist of the argument is that in OOP, one cannot change the cardinality
of a mutator function. In other words, I can't change addFoo() to
addFoos(), or put tack an additional addFoo() function onto a base type
through extension. In XML Schema you can, in essence, violate the
cardinality restrictions of an element of a base type, so long as the new
elements are distinct _in position_ from the original (constrained)
occurrence.
So how would you model such a datatype extension in an OOP language? Not
naturally, that's for sure.
