[SWSL] Teleconference minutes for May 13 2004

apologies for late posting ...

Minutes of SWSL teleconference May 13 2004

Attendees:
Michael Kifer
David Martin
Sheila McIlraith
Rick Hull
Daniela Berardi
Steve Battle
Bijan Parsia
Benjamin Grosof
Michael Gruninger
Jienwen Su (new member)

Review of upcoming F2F agenda:
Sunday, 23 May:
1200-1300	Registration
1300-1330	Plenary Session - Administrative Remarks
1330-1500	SWSA and SWSL Sessions
1500-1530	Break
1530-1800	SWSA and SWSL Sessions

Monday, 24 May:
0830-0900	Registration
0900-1030	SWSA and SWSL Sessions
1030-1100	Break
1100-1200	SWSA and SWSL Sessions
1200-1300	Lunch
1300-1500	SWSA and SWSL Sessions
1500-1530	Break
1530-1700	SWSA and SWSL Sessions
1700-1800	Plenary Session - Outbriefs
1800		Adjourn

Sunday will be use for presentation of the remaining straw proposals. 
On Monday we
are keeping the time open (and unstructured for now) for discussion of 
the straw
proposals.  For those who can't come, teleconferencing will be possible.

=====

FLOWS (straw proposal) presentation -

See presentations slides linked from here:
   http://www.daml.org/services/swsl/straw-proposals/

[Note: The presentation itself is not captured here, but (most of) the 
questions,
clarifications, and discussion is captured.  Apologies for sketchiness.]

Sheila presenting (slides 1-12)

Benj Q:  what does "explicit repn" mean for msgs/dataflow
- would generic FOL/rules lang qualify, with just a set of predicates in 
that?
A:  yes

slide 4 =
BG: drawbacks of FOL include:
   not extensible to nonmon
   commercial reasoners not well-developed

slide 5 -
Question: what's the relationship between PSL and first-order logic (FOL)?
SM: PSL is all first-order, but with a non-standard model
   complex actions are first-class objects
MK: Golog is a programming language; PSL is not

BG: what is "writability" (on the slide)?
Answer: "writability" is guidance on how to most effectively express things
Comment: PSL is expressed in KIF; not a Web language
Comment: PSL is lacking in modularity

slide 6 -
Note: WSC on slide 6 means WS Composition
Q: how is nonmon brought in?
A: FLOWS is a language in which other types of reasoning can be projected
Comment: circumscription is awkward, starting with FOL
SM: use circumscription to understand the semantics (only)
BG: predicate completion, stratified logic programs can be captured using
circumscription
SM: answer completion - work ongoing beyond LP; finding nice solutions 
to closure issues

Q by Benj and Michael K:  how do you hope to map nonmon formalisms into FOL?
A:  one way is to add a 2nd-order circumscription axiom, then show for 
example
that it's equivalent to a predicate completion, a la Reiter approach to
solving the frame problem

Michael G:  the idea is that FLOWS has a first order ontology and first
order statements, but reasoning -- e.g., nonmon -- could be in a
non-FOL logical KR

Benj:  i.e., can PROJECT other reasoning, e.g., nonmon, into FLOWS FOL?
A: yes, that's well put

discussion: can represent predicate completion / stratified LP / answer
set programming / othre circumscriptions in this way, using some known 
results

slide 7 -

BG: Isn't this proposal somewhat polyannish?
SM: yes
BG: there are *too many* results; worried that FLOWS doesn't represent any
decisions; more guidance will be needed; each task is really hard
MG: more emphasis on rep. than reasoning
MG: tension between high-expressive and lack of effective reasoning; 
looking for
median: start with expressivenss; look for tractable subcases

slide 10 -

MG: ontology aspect of FLOWS: identify subset of PSL corresponding to 
owl-s,
extended with messages, dataflow, negotiation (potentially ext of PSL)

MG: But PSL has ignored messages
RH: We will commit to a particular approach

will map concepts from OWL-S into a subset of PSL,
plus represent/map some other things like messages into an extension of PSL
- have to decide exactly how to do that ontologically

Benj Q/obs:  isn't there a tension between using generality of FOL to
represent existential consequent expressions, e.g., on slide 13,
versus keeping things simpler wrt fitting into LP or tractability?
E.g., would it be OK here to skolemize?
A:  yes, there's a tension, we have work to do

slide 11 -

Michael G. presenting (slides 13-16):

slides 13-15 -
BG: how much violence would skolemization do to your approach?
MG: good question; analogous to considering a prototypcial occurrence; 
implies
reasoning by cases
BG: some of these decisions will have important implications re: 
reasoning, tractability

BP: What's the relationship between these descriptions and services? 
What's the
relationship to golog?
MG: buy_product is a service
process descriptions can be considered generalizations of golog programs
constructs in golog are macros for temporal formulas - which can be 
directly
specified in PSL

Q: How to represent equivalence between 2 different services?
A: equiv. relation would be yet another macro in golog

SM: FLOWS is nicer than golog from a formal perspective
golog didn't go deeply into model-theoretic semantics

slide 15 -

Benj comment: overall, I'm worried that for putting out standards proposals,
we want to be incremental up from what we know how to do in a scalable
and practical way, including scalability from viewpoint of authoring
(of service description knowledge) not just of computation
- Michael G:  we started up from the scenarios
- Benj:  those aren't necessarily the scenarios that we should weight most
heavily, if we don't know how to do those scenarios in a scalable practical
way

Michael K Q:  will these service descriptions be generated from
programming code, i.e., from executables?
A:  good question!   but don't want to be restricted to executable, of 
course

Michael K:  suppose we have a language that is executable and do
simulation of execution in that -- rather than more general reasoning?

wrt tractability:
Benj:  we should identify what are the already known tractable cases
Michael G:  yes
Benj Q:  what about FSAs, for example -- when are they tractable?
Rick A:  yes, we're looking at that; often exponential time; but
worst-case exponential time sometimes is practically tractable,
e.g., Description Logic techniques in Daniela's approach
Sheila A:  also depends whether the exponential parameter is big in 
practice,
e.g., classical planning technique application results today;
e.g., in WS Compositon argue often are working in very broad but
very shallow trees -- which keeps the practical search space small enough

Rick Hull presenting (slides 17-end):

slide 17 -

PSL approach allows to quantify over complex activities
can embody FSAs into psl

slide 19 -
BG: head existentials might be problematic
RH: there are some constructs that don't naturally go into LP framework; we
may not need all of LP
BG: some tasks use LP, but
reachability, e.g., might be beyond LP

BG: ontological commitments in FOL - that's nice,
but commitments to sublanguages will be needed (to be useful and taken 
seriously)

MG: FT usecase - realistic scenarios call for expressive approach
BG: historically FOL efforts haven't gotten very far:
   authoring
   scalability
should start with what we know how to do; then work towards more 
generaility.
beware scenarios that require reasoning that's not well-understood
MG: this is not a lang looking for problems - we are starting from use cases

MK: how do you envision these specs (slides 15, 19)? statements about a 
C program?
executable?

RH: expressions or assertions
MG: The goal here is to reason about services; not embed SWSL into 
implementation
(so not necessarily executable)

MK: could be both executable and support reasoning

RH: requirement that everything reducible to an exec. spec isn't good
e.g. CDL is not executable.  SWSL should embrace everything CDL can express.

MK: FOL a non-starter; looking for subsets
what if we have an executable language to permit simulation?

MG is simulation more tractable?
MK: yes

MG, SM, BG: simulation is another kind of reasoning

BG: It's hard to sell "tractable subsets to be named later"

MG: tractability can talk about tractability of different *theories* 
(class of
processes)

BG: FSAs: reformulated, will be tractable

MG: weakness - computational subclasses not identified

Q: under what circumstances are FSA (BS) tractable

RH: exp. time algo. is pragmatically tractable
worst-case is exponential
pragmatic question: heuristics

SM: planning is pspace or np-complete
but large problems are handled very quickly
search space for WS composition tends to be small

BG: deep KR - XML - presentation

The Who:

Bijan Q/issue:  who's going to write/author SWSL descriptions?
Rick A:  the kind of person who will write WS Choreography
Bijan Q:  are there more people working with process algebras than
with FOL for process specifications?
Michael K:  way more are familiar with FOL altogether
Michael G:  in case of PSL, it's the s/w vendors
Michael G:  for SWSL, will it be service providers writing SWSL?

Benj:  we can call this issue: conceptual familiarity for target authors;

David:  let's identify issues for discussion at F2F

Benj:  who is the target author community would be a great one,
I think that should
include service providers not just s/w vendors

Received on Thursday, 3 June 2004 19:34:11 UTC