Re: New version of walk-through available

From: Jeff Heflin (
Date: 01/09/01


The last two weeks have been really hectic for me, so it isn't until
recently that I had a chance to give the Walkthrough and Reference a
detailed look. Sorry they're so late, but here are my comments:

Reference document:
1) Imports: I think we need to explain to the reader why we have
imports, and what it gives us that namespaces don't. That is, the
namespace rec does not imply anything about definitions of terms, and
even if we say that it should for DAML, there are a number of of valid
ontologies that will provide new definitions without introducing new
names (they add to the definitions of terms provided in other
documents). Theorectically, we could augment the import mechanism to do
what namespaces give us (since, if you import definitions, you obviously
mean to import the names they apply to as well), and get rid of
namespaces, but since we live in XML world, I guess we're stuck with

2) Property Elements: Don't UniqueProperty and UnambiguousProperty
specify global cardinality restrictions? That is, no matter what class
the property is applied to, the cardinality constraints must hold,
unlike the various "cardinality" properties used in a Restriction. I
think we should be clear about the differences between these two types
of cardinality restrictions.

3) Appendix - List of language elements: It would be nice if this was
sorted alphabetically and hyperlinked to the appropriate descriptions of
the elements in the document. That way, someone can easily look up what
a particular element means.

Walkthrough document:
1) Housekeeping: We might want to say a little bit about why we need
imports, as I mention above.

2) Defining properties: We might want to say what it means to have
multiple domain restrictions

3) Defining properties: (concerning comment about better alternative for
domain and range restrictions). After having thought about this a while,
I don't think we should necessarily say the use of "Restriction" and
"toClass" is better than "domain" and "range." I think there are pros
and cons to both and we should simply present these to the reader so
he/she can decide on a case by case basis. Pros for domain and range
include ability to be grokked by normal RDF agents, and the fact that
sometimes maybe you really do want to restrict the property globally.

4) Defining property restrictions: "Such an assertion about the class
Animals has exactly the SAME STATUS as the assertions made within..." I
think we should clarify that if such assertions are made from another
document, then they only have the same status if the other document is
equally trusted!

5) Notations for properties: See my comment for the reference about
UniqueProperty and UnambiguousProperty specifying global cardinality
restrictions. We should probably point this out here as well.

6) Notations for properties: "... not yet that Ancestor is the
transitive version of hasParent ... We would need to introduce
additional elements to enforce these connections." This means that DAML
doesn't yet have the expressivity for this, right? If so, can we make
that a little clearer?

If any of these are controversial, maybe we can discuss during the
telecon today.


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