[Interface-dev] Tagged values

[Stephen Waterbury]

Zope Interface gurus:

So far, I've read some of the z.i source, the introductory docs, and
played with it.  Right now I'm only concerned with Attribute
and Interface, and as far as I can see, no harm is done by giving
them direct attributes instead of tagged values for such things as
are shown in the README example ('author', 'date-modified').

Is there some side-effect that I haven't thought of, or were
tagged values introduced mainly to avoid possible user confusion
of a direct attribute of an Interface with a contained Attribute
instance?

Also, in reading the UML spec, it appears to me that the UML intent
for tagged values (which z.i's docs says is the model for z.i's use
of them) is to be "semantically significant" extensions -- by which
I think they mean semantically significant at the same meta-level
as the interface specification.  But such things as the "author"
and "date-modified" of an Interface or an Attribute are not
semantically significant at the level of the Interface's
specification, so I don't think the concept (at least as it's
illustrated in the z.i README example) is the same as the UML
tagged value concept.

My main question here is whether there are any known gotcha's to
giving Interface and Attribute (and other Elements) direct
attributes.

Thanks!
Steve