- From: Dave Reynolds <der@hplb.hpl.hp.com>
- Date: Tue, 30 May 2006 15:01:25 +0100
- To: Paula-Lavinia Patranjan <paula.patranjan@ifi.lmu.de>
- CC: public-rif-wg@w3.org
Hi Paula, >> o As already stated I would prefer the third goal to be "Basis for a >> future semantic web rules language". This would imply support for >> requirements such as: >> http://www.w3.org/2005/rules/wg/wiki/Standard_RIF_must_be_able_to_expres_RDF_deduction_rules >> which are not currently included. >> > First, the third stated goal, 'W3C Consistency', is more general than > your proposed goal and it expresses excatly what we need for RIF. > Second, I don't think that our goal in this WG is to develop a basis for > a future Semantic Web rule language, but to enable interchange between > existing and future (Semantic) Web rule languages (this is different in > my opinion). Agreed, it is different, that's the point. The question for me is whether the working group wants this as one of its explicit goals. What I hear from many people, though not everyone, is "no". However, I would like to get this goal explicitly considered and adopted or ruled out and if ruled out I'd like that decision to be written down somewhere in a form that can I reference as part of my recommendations back to HP. > The text below the diagram is not complete yet; that is why the support > of RDF deduction rules is missing, but this comes actually under > 'Support RDF'. OK I'll wait to see that. >> o 1.1.c Meta language features. I'm unsure about this on several levels. >> First, why does this appear under "no surprises"? To me it seems only >> related to coverage. Second, priorities seem like a different issue >> from meta-level rules, perhaps they should be separated. Third, I'm >> not convinced that general metalevel rules really fall above the cut >> line for us before phase 3. Fourth there needs to be "opposes" links >> from this to at least "low cost of implementation"; doesn't this also >> make ruleset combination hard? >> > Regarding your first comment: Take as an example a set of rules where > priorities are used; if through interchange this information is lost > then you get a kind of surprise in the sense that 'unexpected' results > might be obtained. That's an argument for "coverage" not for "no surprises". > Regarding your second comment: You're right, they are different...but at > the same time one can consider that they express some meta-level > features; so, for keeping the diagram as simple as possible we consider > them falling in the same category. OKish. > To your third comment: the proposed DC diagram and the whole work we > have done on goals, CSFs, and requirements do not take the different > RIF Phases into consideration. I wasn't just commenting on phasing but on where the cut line goes. I can see that priorities are needed for coverage but am not yet convinced that general meta-level rules are within scope for the current charter. >> o I don't understand the phrasing of 1.1.a Formal Semantics. The text >> seems to be about multiplicity of semantics in which case there needs >> to be a separate requirement that RIF Core should have a (i.e. at >> least one) formal semantics. The phrasing is unclear on whether this >> is addressing RIF Core or the sum of RIF dialects, if the proposal is >> that the Core should itself not be "unitary" then that needs to spelt >> out more clearly so we can argue about it. >> [Actually, difference between RIF Core and RIF dialects us unclear at >> several places in the text.] > As mentioned above, the DC proposal does not differentiate between > different RIF phases or RIF core and dialects. I think it is best > leaving this separation for future work, say after taking a decision on > the overall DCs. So, the requirement states the need for multiple > semantics for RIF but gives no information on which RIF is meant here. By the end of the f2f I assume we'll want to be quite clear on what is actually in the Core and whether it is a rule language with a single semantics, a rule syntax with a set of semantics, or a set of components (such as a condition language) from which rule languages can be constructed. Perhaps that is mostly design rather than UCR but *if* we were to adopt the "basis for a semantic web rule language" as a goal then that might support a need for a "unitary" semantics for the core. > However, I agree that the text needs refinement and I'll do that > together with Frank in the next days. OK, I'll await the new text. >> o Markup of semantics. I guess I still don't understand what people >> mean by this phrase. Is this supposed to be: >> (a) machine processable definition of the semantics in some general >> formalism like an operational semantics? >> (b) metadata tags attached to symbols to distinguish divergent use of >> apparently similar symbols (e.g. ->)? >> (c) different symbols for constructs with different semantics so that >> each symbol is unambiguous? >> (d) any and all of the above? >> > In my opinion, markup of semantics does not refer to the items listed > above. This requirement states that there is a means to specify the > formal semantics of a rule set to be interchanged so that the system > using this rule set through RIF knows about its formal semantics; this > does not mean that the algorithm for evaluating the rule set comes with > the interchanged rules. Good. > It might well be just a URI where the > specification of the rule set's formal semantics is given. Also, such a > formal semantics is to be attached only to rule sets. That's fine by me and is an example of what I meant by (b). >> Lesser comments: >> >> o Why is "Support XML" linked to "Extensibility"? That doesn't seem >> intuitive to me and I couldn't spot the explanation in the narrative. > I think Frank can explain best this link :) >> >> o Conformance model. I've not yet seen an example of when a default >> behaviour other than "ignore ruleset" could be used and question the >> linking of conformance model to the "default behaviour" proposal >> (which currently only has one named champion). > The conformance model is more general than just 'ignore ruleset'. It > also relates to the multiple formal semantics for different rule sets, > e.g. in case one needs to combine two rule sets with different > semantics. There are also other examples such as interchange between > systems supporting priorities for rules and systems without such support > where other conformance models than just ignore rules could make sense. Perhaps I was reading too much into the link to the "default behaviour" requirement. I assume there is then a need for someone to edit a page on a conformance model requirement. Dave
Received on Tuesday, 30 May 2006 14:01:51 UTC