breakout session: classification of rule languages
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at First F2F, San Francisco, 9th of December 2005

chaired by Chris Welty
scribe: Pascal Hitzler

- Welty:
  there will be clusters within which interoperability is good and desirable
  between clusters interop will be limited.
  thats for phase 2
  phase 1 only horn, so probably no problem

- Hitzler, Grosof: phase 1 probably not so easy

classification dimensions brainstorming:
========================================

"Market Segments"
- Relational DBMS
- PR-SR
- ELA
- Prolog
- controlled english LP

"Expressiveness"
- FOL vs. Modality
- Decidability
- vs. uncertainty
- vs. Logic programming (LP)

"Semantic assumptions"
- CWA (closed world assumption) vs. OWA (open world assumption)

"Support Features/Implementation of system"
- inference control: 
  backward vs. forward
  incremental vs. exhaustive
- authoring
- analysis/testing
- comments 


opinions (not necessarily chronological) raised while brainstorming:

- will priorities etc. play a role?
- Kifer: syntactic vs. semantic classifications?
- Barkmeyer: CWA/OWA distinction may be difficult
- Chapin: what about linguistic logic?
  has to do with grammar as in linguistics
  may be market segment
  e.g. controlled english LP
- Hitzler: need OWL ontology to classify rule systems
  (wide agreement on this)
- Hitzler: Procedural attachments?
  Welty: Is feature, shouldn't be used in classification
- Welty: Are these support features important for us?
  Grosof: secondary at this point, but still important.
  Welty: Its metadata.
- Engel: What's should be the result of the WG? Joint syntax?
  Grosof: Don't quite know. Probably difficult.
  Kifer: probably common syntax not even possible, e.g. different logical
connectives 
  Welty: alternative: one syntax construct with annotations which tell which
semantics is meant
  Welty/Kifer: clear that we will have different semantics
- Menzel: probably better focus on something small rather than branch out as
we do now, i.e. build RIF bottom-up in an incremental way?
- Grosof on historic approaches:
  SWRL: LP syntax (with FOL semantics) on top of OWL
  SWSL: Expressiveness of both LP and FOL at disposal
- Chapin: Why not use FOL/LP distinction as start for design of RIF?
- Welty: building OWL ontology of rule languages.
  which properties
  which key differences (discriminators) to split things up?
  see below
- Kifer: should have semantics vs. syntax table. 


for an OWL rules ontology:
--------------------------

discriminators:

- open vs. closed
- FOL vs. other semantics
- non-monotonic?
- forward/backward chaining
- procedural vs. declarative
- decidability
- complexity
- modality/intentionality

- Welty: 
  lets start with this list and elaborate on it
  calls for suggesting an ontology
- Menzel: 
  reuse some other similar work already done?

Hitzler sends notes to Welty.
Everybody proposes taxonomies.
Set up Wiki page.
Hitzler sets up the Wiki page: RifClassification.

[End of session/Welty has to leave]

post-discussion:

- Grosof:
  can we work bottom-up in parallel?
  proposes Horn plus Lloyd-Topor
- Chapin: what about using common logic? SBVR is fragment of it
- Grosof: doesn't like some non-FOL features of common logic
- Grosof: could also use FOL RuleML