Errata Ch 2. Classes - http://www.w3.org/TR/rdf-schema/#ch_classes

While the first paragraph of chapter 2 "Classes" is good and concise, I
have an issue with the whole second and third paragraph. I don't think
they are necessary. The points raised in the 2nd and third paragraphs
could be incorporated into an extra sentence of the first paragraph
without introducing confusion. The second paragraph is:

    "RDF distinguishes between a class and the set of its instances.
    Associated with each class is a set, called the class extension of
    the class, which is the set of the instances of the class. Two
    classes may have the same set of instances but be different classes.
    For example, the tax office may define the class of people living at
    the same address as the editor of this document. The Post Office may
    define the class of people whose address has the same zip code as
    the address of the author. It is possible for these classes to have
    exactly the same instances, yet to have different properties. Only
    one of the classes has the property that it was defined by the tax
    office, and only the other has the property that it was defined by
    the Post Office"

1. Do you really need to state that there is a distinction between a
class and its instances? The first paragraph already makes this as clear
as it needs to be.
2. "class extension" is used 1 more time in this doc. And its use there
is unnecessary there. This term does not need to be introduced and is
just confusing.
3. The example is really quite perverse and hard to follow. Your trying
to get across that instances can have more than one class? I.e. "You
know multiple inheritance? Well its like that.".

I also have issue with the third paragraph of this chapter:

    "A class may be a member of its own class extension and may be an
    instance of itself."

Are you saying the same thing twice? I.e. a class is an instance of its
"class extension" if and only if a class is an instance of itself. This
is an esoteric feature of the definition, and I don't think it is
generally useful knowledge. Its made obvious later in the description of
rdf:Class.

In summary, I propose you remove the second and third paragraphs  and
add this senctence to the first:

        "Resources may be instances of more than one class."

Thanks,

Sam.