RIF Telecon 8 May, Agenda: http://lists.w3.org/Archives/Public/public-rif-wg/2007May/0011.html -- 8 May 2007

<ChrisW> Meeting: RIF Telecon 1 May 2007

<sandro> can you hear me at all now?

<Harold> Zakim [NRCC] is me.

<ChrisW> scribenick: DavidHirtle

<ChrisW> Scribe: David Hirtle

<PaulVincent> Thanks Dave! I so enjoy my little chats with Zakim...

Admin

F2F6

chris: anyone who hasn't filled out the survey for the F2F, please do so

<PaulVincent> Unless dinner is ++ better than the meeting...

chris: 22 people who will attend the meeting, and 28 who will attend the dinner...

sandro: make your hotel reservations soon if you haven't already

Liason

<PaulVincent> NO update from PRR

<ChrisW> POWDER working group

chris: POWDER is another SemWeb WG working on content rating...

<AxelPolleres> interesting, that fits with one of our use cases.

chris: they've identified some rules use cases and want some feedback from us
... I'll forward to our list; feel free to reply

Core: Issue 31

<sandro> Axel: I sent comments on SPARQL that could perhaps been endorsed by RIF. For now I just sent them as myself.

<sandro> Chris: Alas, we didn't have time to make that formally from RIF.

<sandro> Chris: I think it's fine.

Issue-31

<ChrisW> http://www.w3.org/2005/rules/wg/wiki/Issue-31

chris: main discussion in the group is between ONDS and OS choices

<sandro> Sandro: translation to DS is hard, from DS is easy.

<sandro> Chris: Straw Poll. Who likes OS?

<AxelPolleres> Can MK comment on that?

<sandro> Chris: translations from lower numbers to higher numbers is easy; not the other way around.

chris: translating from a higher number choice back to lower number (esp 3 to 1) is hard

hassan: why is it difficult to translate from higher number to lower?

<AxelPolleres> That was a question.

<DaveReynolds> Actually #2 (ONDS) to #3 (OS) is not quite trivial if you have equality

<AxelPolleres> what hassan mentions is 2 -> 1, that is easy.

<DaveReynolds> agreed 1 <-> 2 is trivial, it is 3 (OS) which makes it hard, both ways

chris: there are some entailments that make it extremely difficult from 3 down to 1 (or even 2)

hassan: if you interpret it then it has a unique meaning; you can spew it out unambiguously

michael: hassan is right, translations in both directions are possible

<sandro> p(a), q(b), p=q, in OS entails p(b) and q(a), right.

<sandro> ChrisW, I'd be interested to hear the results of the straw poll, but I'd like to know if folks can vote for more than one option.

<Hassan> OSR is even better IMHO

chris: michael, from OS into DS is easy?

michael: depends on what you mean by easy; can use a predicate etc.

<sandro> MichaelKifer: it was proven in the HiLog paper ...

<sandro> Chris: a predicate for each arity ... a combinatoric explosion of rules.

hassan: where's the combinatorial explosion come from?

<sandro> Hassan: please explain combinatoric explosion

michael: number of rules

<sandro> MichaelKifer: grown in the size of each rule, but the same number of rules, same number of symbols. I think the grown is actually linear.

sandro: if no one is going to argue other side, no need for argument

chris: yes, vote for more than one if you're happy with that
... or we'll just ask who is against
... who's opposed to choice 3 (OS)?

<sandro> (say "-1 OS" if you are opposed.)

<sandro> (no one opposed)

chris: anyone opposed to 2 (ONDS)?

<sandro> -1 ONDS

<MichaelKifer> -1 onds

<DaveReynolds> preference against ONDS but not rule it out

hassan: I'm opposed to it

<sandro> -1 DS

chris: who's opposed to DS?

<AxelPolleres> -1 DS

<PaulaP> -1

<Hassan> hak -1

<MichaelKifer> -1 ds

<sandro> Allen: -1 DS

chris: so no one's opposed to 3; sounds like consensus

sandro: hassan seems to prefer 4, but we don't need to choose now: can just add reflection later

hassan: better to have reflection from the start, especially if it's not too costly to add

chris: is there an encoding of a reflective rule (rule that takes the syntax of the language and puts it into the language)?

michael: I don't know; haven't discussed it

sandro: by picking 3, we're not ruling out 4

michael: we need to pick up one and define semantics accordingly

sandro: have you thought about semantics of 3 vs 4?

michael: I know how to do semantics for 3 etc. but there are options for 4 (even syntactic)... we cannot just leave it open

chris: I agree with that; we should agree on 3 or 4

<sandro> Hassan: Reflection is the possibility to describe your abstract syntax in your semantics.

<sandro> MichaelKifer: How much introspection do you want to allow?

<Harold> Pat Hayes recently put forward the very

<Harold> general IKL system

<Harold> which may be of interest here

<Harold> regarding syntactic self-description:

<Harold> http://lists.w3.org/Archives/Public/public-rif-wg/2006Oct/0109.html

sandro: let's resolve on 3 or 4 for now and discuss it more next week

chris: sure

<sandro> MichaelKifer: introspection for encoding rules as data isn't a problem, but if we get close to Liar Paradox, etc, then it's another matter.

michael: I'm concerned about what happens when we go into a first order dialect

<sandro> MichaelKifer: so it's easy enough to have some quotation, but if we get extended to FOL it may cause problems.

<Harold> How much would we go in the direction of KIF and CG if we introduce quotation mechanism?

michael: a first order extension of this could lead to paradoxes, e.g. whatever I'm saying is a lie

hassan: a very simple reflection mechanism can't harm you

michael: I don't know what the consequences are going to be if we allow reflection in the core; in a dialect only, it's not a problem

hassan: if you're designing a language, having the possibility to describe your own syntax is an advantage
... I don't see any dire consequences

michael: in FOL, if you allow self-reference, you have to be very careful

<Harold> Could we have a 1st-order-capable Core and a (Reflective) Extension Layer above it, of possible use for some Dialects.

chris: everyone seems to be talking about a different aspect of reflection
... hassan, could you write up a proposal about reflection you have in mind?

hassan: sure, but I'm just using general programming language notion

<sandro> hassan: I'm talking about something like Prolog's "univ" ( written "=.." ).

<sandro> Chris: My concern is whether there is a way to support that in things like FOL.

hassan: a language that does not support reflection doesn't have to worry about it

<sandro> Chris: We're trying to make the the Core be something that can be translated to every other languages.

chris: yes, it does, in order to be compliant

sandro: concrete example: we have a ruleset and we're translating it to FOL ... if the rule is trying to infer new data, does it affect rules themselves?

chris: anyone else in favor of adding reflection to Core?

(no one)

chris: hassan, please send a message to the list and we'll discuss next week
... if no other support, we'll have to move to a dialect

sandro: let's resolve that we agreed on 3 or 4, not 1 or 2

hassan: I won't object to 3; I won't be able to attend next week

<PaulVincent> I'd be interested in reading Hassan's arguments for 4...

michael: I won't be on the telecon next week either

<sandro> PROPOSED: To go with 3 or 4, and next week we'll decide between 3 and 4, if Hassan's e-mail convinced anyone.

<sandro> PROPOSED: To go with 3 (OS) or 4 (OSR), and next week we'll decide between 3 and 4, if Hassan's e-mail convinced anyone.

chris: any objections?

<sandro> RESOLVED: To go with 3 (OS) or 4 (OSR), and next week we'll decide between 3 and 4, if Hassan's e-mail convinced anyone. (cf http://www.w3.org/2005/rules/wg/wiki/Issue-31)

Core: Metadata

chris: I'm not really prepared on this issue; christian not here

sandro: I feel somewhat prepared
... DaveR may be more than me if he'd rather

DaveR: I took issue to be that we have requirement about attaching metadata to rules... how do we represent, what are core items, etc?

<sandro> DaveReynolds: How do we represent Metadata? What core vocab should we have? And How extensible should it be?

<sandro> DaveReynolds: I think it should be, in the style of RDF, completely open ended.

<sandro> Sandro: what if you use RDF in RIF Core format?

<Hassan> BTW: having meta-data is having some relection

<sandro> Chris: So what if you have a rule like "All the rules authored by Chris are false" ?

chris: we have to be careful about putting this in core because of problems in translating rules into languages that don't support it

<sandro> Sandro: How about having a file have a Ruleset and a Metadata set, and you can merge them at your own risk.

chris: one obvious way to express RDF as metadata would be to use triples
... what metadata do we need?

<sandro> 4.1.5. Embedded metadata

<sandro> RIF must support metadata such as author and rule name.

<Harold> A 'rulename' can be used to *attach* metadata to rules such as 'author'.

<PaulVincent> Rule metadata - see Dublin Core; properties like priority etc

<sandro> Chris: just wondering about kinds of metadata that might impact the core.....

<sandro> DaveReynolds: date, provenance,

chris: is Dublin Core enough?

<sandro> DaveReynolds: for round-tripping, we might need "the original form of name"

Paul: usually in rule-matching systems, data defined for customer

<DaveReynolds> +1 to Chris, translator hint annotations seem valuable

Paul: obvious one is original language in which rules are defined, also source rules as comments

chris: we have this Dublin Core metadata, round-trip "preservation metadata", any other kinds?

allen: dialect identification metadata?

sandro: I don't think that's metadata

Harold: instead of giving dialect as metadata, could have different URLs pointing to different XML Schemas of RIF

<DaveReynolds> Harold - surely a URL refernce is just a form of metadata?

<PaulVincent> Reference: http://dublincore.org/

sandro: I agree, could have different namespace for each dialect

harold: XSD is quite weak; may involve other things like Schematron or even semantic validators (for results of static analysis)

<Harold> Dave, I meant the URL that points to the definition of a dialect such as to its xml schema.

chris: does each dialect define set of metadata fields?

<Harold> Chris, about the direction of pointing between a RIF file and its metadata, I think essential metadata (about results of static analysis) cannot point from outside into their RIF file -- they must be attached to the ruleset iteself.

<ChrisW> ack

UCR

chris: where do we stand?

allen: need to add text for figures, otherwise nothing else

chris: should we have a use cases section at F2F?

allen: phase 2 requirements...

chris: I think Paula started a list of phase 2 requirements

AOB

allen: I did the ontology thing using imports and sent it to the list a while ago... just wanted to make sure it's okay

<AxelPolleres> Suggestion: Can we postpone this discussion until in two weeks (will be)

<AxelPolleres> travelling next telecon!

RIFRAF

chris: sure

<AxelPolleres> yes!

chris: so schedule F2F time to talk about RIFRAF

<AxelPolleres> sorry, cannot unmute, my skype is somewhat stuck

<Hassan> +1

<AxelPolleres> please schedule rifraf on day 1 (june 2)

<AxelPolleres> thanks!

<ChrisW> Chair: Chris Welty

- DRAFT -

RIF Telecon 8 May, Agenda: http://lists.w3.org/Archives/Public/public-rif-wg/2007May/0011.html

8 May 2007

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