From: Sandro Hawke (sandro@w3.org)
Date: 11/06/02
(Harold, you mentioned that you had replied to my message from last
week about coming up with a single unified XML & RDF/XML syntax, but I
haven't seen it. It is perhaps superceded by last night's discussion
and this message.)
Thanks for the presentation yesterday. I had to leave about 5:05
EST, before the meeting actually ended. I imagine I missed the most
interesting comments; were any decisions made?
Despite my experience doing very similar work, I'm still impressed by
how tedious both the XML and the RDF/XML serialization are. I had to
remind myself that this is like looking at the assembly-language
output of a compiler: it's important to get right, and then no one but
tool-builders should ever have to see it again.
With that in mind, maybe using a single, canonical RDF/XML
serialization, no matter how hideous it's likely to be, would be
best. (I'm imagining an RDF/XML serialization which is constrained
to specific choices about use of type-nodes, etc, so that it's
amenable to processing by XSLT and other non-RDF tools. I assume
that's important to your user base.)
I'd love to see you follow the convention of uppercase names for
classes and lowercase names for predicates; I find it makes the
striped syntax much more readable. You seem to be trying to have the
RDF/XML syntax look like the XML syntax with a few added bits; I don't
see much reason for that; either think in XML or think in
graph-syntax.
Can we get rid of ruleml:cdata, and just map the non-RDF RuleML
identifiers into RDF identifiers? In your slide 11 ("striped
serialization"), instead of
<rel ruleml:cdata="discount"/>
one could use
<rel href="&someNameapce;discount"/>
This does require the "ur" logics to be understood, though; perhaps
that's an unacceptable burden. Some provision (probably using
%-escaping) would also be needed for non-URI-char names).
My big question (was this addressed after I left?) is Benjamin's
original one: is RuleML the right starting point for RDF Rules (aka
DAML Rules)? Personally, I'm waffling over whether its additional
complexity is desirable or not. It's hard to know.
A simpler approach might be something like having XML tags <Rule>,
<if>, and <then>, and inside the "if" and "then" clauses one can put
arbitrary RDF/XML (aka DAML). There would also need to be a way to
mark variables, and to convince people it's okay to use RDF/XML in
this quoted (not asserted) manner. TimBL suggested parsetype="quote"
for this, which would the whole thing RDF again, except for indicating
variables. (In this case, we need to indicate both existential
variables and universal variables if we want Horn expressivity; we
have no functions, but we can de-Skolemize the functions into
expressions using existentials scoped to the consequent.)
-- sandro
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