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chair's projected slides from F2F3

From: Sandro Hawke <sandro@w3.org>
Date: Sat, 10 Jun 2006 09:04:02 -0400
To: public-rif-wg@w3.org
Message-Id: <20060610130418.7B9BA4EFAA@homer.w3.org>


I converted the powerpoint slides [1] to plaintext [2] and added a few
notes in double-square brackets [[ like this ]].  There were some
changes made after this version -- such as to include the requirement
that RIF have a small number of standard dialects -- but unfortunately I
don't have a copy.  Would someone who does please edit this plain-text
version to include those changes?

   -- Sandro

====================================================================

[[ In general slides begin with a proposed requirement as it occured
in the editor's draft from before the meeting and end with a
disposition, such as a rephrasing, a postponement, or a note that the
requirement is subsumed by some other requirement.  Intermediate
rephrasings and notes are kept. ]]

Goals, CSF, Requirements
 

Formal semantics 

    * Where rules are interchanged between different tools and across
      language boundaries, assumptions about the meaning of the rules
      can be dangerous and difficult. A formal semantics framework
      will reduce the potential for error in the exchange of rules in
      such and may other situations. 

    [[ No one was able to define "formal semantics" clearly for the
    group, but there was a sense that restricting ourselves to
    "model-theoretic semantics" was not acceptable. ]]

    * Clear and precise semantics

    * Phase 1

Multiple semantics

    * RIF should be able to cover rule languages with different styles
      of semantics, e.g. 

       - Operational and declarative

       - Stable and well-founded and...

       - Fixed-point and...

    * RIF should be able to cover rule languages with different
      intended semantics for the rules 

    * Phase 1 (understand extensibility)

Markup of semantics

    * A 'no surprises' rule interchange is only possible if the
      original semantics of the rule sets to be interchanged is
      specified. Thus, a means is needed for specifying which formal
      semantics the rule set to be interchanged has. 

    * RIF has a means specifying the intended semantics of the
      interchanged the rule set 

    * The intended semantics of the rule set in a RIF document should
      be characterised syntactically 

    * RIF should have a standard way to specify the intended semantics
      (or semantics style) of the rule set in a RIF document 

    [[ This is perhaps an obvious conclusion of the previous
    requirement.  How could RIF cover languages with different styles
    of semantics while not conveying the information about which
    semantics are to be used?  The group decided to err on the side of
    redunancy here. ]]

    * Phase 1

Meta language features  

    * RIF should support meta language features such as priorities and
      preferences 

       - Priorities and preferences are semantic annotations => go
         under previous req 

       - Discriminator => goes into rifraf

    * meta rules for meta reasoning

       - Language feature

       - Goes into RIFRAF

    * Phase 2

Meta data 

    * RIF should support meta data

       - E.g. author, rule name

    * Phase 1

No Title

    * The RIF should support first order deductive rules

       - RIF Core must support deduction rules

       - RIF Core must cover pure Prolog (dropped)

       - Extended RIF must cover FOL

    * The RIF should support normative rules

       - Standard RIF must support normative rules

    * RIF should cover deduction rules

    * RIF should cover three different classes of rule languages,
      specifically: deductive (LP and FOL styles), normative, reactive 

    * Phase 1 : deduction rules (with clarification, action paula)

    * Goes into rifraf

No Title

    * The RIF should support Prolog-like rulesets. See Standard RIF
      should be Prolog-like but not Prolog-compatible . 

       - dropped

    * The RIF should cover production rules and ECA. This includes all
      the major classes of production rule-like systems such as
      RETE-based systems and Event Condition Action rule-based
      systems. See Extended RIF must support production rules . and
      Standard RIF must support reactive rules 

       - Phase 2

       - RIFRAF

Combined rulesets  

    * The RIF should support rule sets that are combinations of
      different kinds of rules (i.e., a mixture of deductive,
      normative, ECA rules and so on.) This may affect the semantic
      integrity of the ruleset language: restricting the kinds of
      semantics that can be ascribed to such combined ruleset. 

    * The RIF should cover rule languages where rule sets can be
      combinations of different kinds of rules (i.e., a mixture of
      deductive, normative, ECA rules and so on.) 

    * Phase 2

    * RIFRAF

Combined rulesets  [[ in a different sense... ]]

    * The RIF should support rule sets where rules are composed of
      features from multiple rule languages 

    * removed

No Title 

    * a condition in a RIF rule may be a SPARQL query

    * A RIF rule should be able to call out an external query

    * (The condition language fragment of) RIF should include an
      extensible mechanism by which rules can consult external
      "blackbox" information sources or query processors. 

    * Phase 2 but may end up with it in P1

No Title

    * RIF should support uncertain and probabilistic information

    * Needs further discussion in phase 2

Support typed languages 

    * RIF should be designed in such a way that it permits the
      incorporation of type system(s) 

    * RIF should cover typed languages

    * RIF should cover rule languages where variables are typed

    * Phase 2

Support oracular models

    * RIF should offer support for models that are oracular, that is
      one needs to ask (a kind of) oracle for finding what the
      interpretation of RIF parts is. E.g. procedural attachments,
      aggregate functions are to be found in this category 

    * Further discussion

       - Removed because covered by the « external calls » requirement

Extensibility of semantics markup

    * The semantics of a RIF ruleset must be specifiable in a way that
      permits the incorporation of new rule languages and language
      features 

    * Syntactic VS semantics extensibility?

    * Dropped (covered under the CSF of extensibility)

Conformance model

    * It must be clear what the conformance profile of a given RIF
      ruleset is and what default processing is implied 

    * RIF must define expected default behaviour

    * Sound reasoning with unknown dialects

       - It must be possible in some practical circumstances for
         systems reasoning with rulesets to soundly proceed with parts
         of their work even when a ruleset contains rules which use
         extensions not known to the system implementors 

    * RIF must specify at the appropriate level of detail the default
      behaviour that is expected from a RIF compliant application that
      does not have the capability to process all or part of the rules
      described in a RIF document, or it must provide a way to specify
      such default behaviour. That default behaviour must be easy to
      implement independently of the rule-processing capability of the
      consumer application. 

    * Phase 1

No Title

    * It should be possible to build reasoners for intended ruleset
      languages without unnecessary burden 

    * Replaced by RIF must be implementable...


No Title    [[ suggested: Compliance Model ]]

    * RIF compliance should not impose compliance with everything in RIF

       - Conformance not in the context of extensibility

       - Needs to be clarified, esp. to avoid trivial compliance

    * RIF will define a compliance model that will identify
      required/optional features 

    * Phase 1

No Title    [[ Well-Understood Techniques ]]

    * Reasoners for RIF should make use of well understood
      implementation techniques. 

    * RIF should be implementable using well understood implementation
      techniques 

    * Phase I

No Title    [[ suggested: Standard Components ]]

    * It should be possible for a RIF reasoner to make use of standard
      support technologies such as XML parsers and other parser
      generators.   

    * RIF implementations should use standard support technologies
      such as XML parsers and other parser generators  

    * Phase I 

No Title    [[ suggested: Translators ]]

    * RIF implementations can be translators from RIF to rule
      languages supported by existing reasoners 

    * RIF should not require rule systems to be changed, it must be
      implementable via translators 

    * Phase 1

No Title   [[ suggested:  Efficient Implementations Possible ]]

    * Low transfer costs (real-time requirements). Be inexpensive in
      representation (cost of transfer and cost of transformation) -
      RIF must be able to accomodate real-time performance
      requirements. 

    * Efficient implementation?  Is this a CSF?

    * Postponed to next WD

Support RDF

    * RIF should accept RDF triples as data

       - Clarification: RIF should cover the RDF data model?

                  May not include b-nodes

                  Binary predicates, uris,

       - RIF should have a mapping from RDF

    [[ suggested title:  Covering RDF data ]]

    * RIF should cover RDF triples as data where compatible with Phase
      I semantics 

       - Sandro and Gary to talk over lunch and confirm consensus to WG

       - Phase 1

    * RIF shoudl cover RDF

       - Phase 2

    * Support RDF/XML syntax

       - dropped

Support OWL

    * RIF should accept OWL knowledge bases as data (to be discussed
      w/ action on JosB) 

    * RIF should cover OWL KBs as data where compatible with Phase I
      semantics 

       - Chris to clarify what to do about OWL in Phase I


No Title

    * RIF should express RDF deduction rules

       - RIF shoudl cover RDF deduction rules (agreement)

       - Should be a RIFRAF classification

       - Phasing TBD as part of RIFRAF

       [[ The portion of RDF deduction rules that fall within Horn
       will presumably fall into Phase 1. ]]

No Title

    * Permit SPARQL queries to be used in rules

       - Pointer to previous req.

       - Covered by external call

       - Phase 2, but...   [[ but it seems easy and a lot of people
         would like it in Phase 1, so maybe we'll try to squeeze it
         in. ]]

Support XML

    * RIF must be able to accept XML elements as data

    * The RIF core must be able to handle XML elements defined by XML
      Schema as data. 

       - Stronger requirement: RIF « translation » of XML Schema
         elements should be those elements themselves 

    * RIF should permit XML information types to be expressed using
      XML schema 

       - Not just data types, e.g. List structures are not xsd
         datatypes (to be clarified -- user-defined datatypes?)

      [[ For phase 1, we agreed to follow the charter on this, I
      think. ]]

No Title

    * RIF will cover the set of languages identified in RIFRAF 

       - We will use RIFRAF to identify classes of languages to be
         covered by RIF  

    [[ By this we mean Extended RIF, of course. ]]

No Title

    * Support LP semantics with negation as failure and strong negation

       - RIF should cover LP semantics with negation as failure AND
         "strong negation as in DLV and courteous".

       - Strong negation is explicitly asserted negation.

       - Needs further discussion, strong relation to RIFRAF

       [[ A running joke of the meeting was around explaining
       "strong negation" as "it's like Classical Negation, but not
       quite".  For a proper explanation see e-mail
       http://lists.w3.org/Archives/Public/public-rif-wg/2006Jun/0087
       ]]

No Title

    * Offer module construct for scoped positive and negation as
      failure queries 

       - RIF should cover scoped queries

       - RIF should cover scoped NAF queries

       - Further discussion Goes into RIFRAF

      [[ presumably Phase 2 ]]

No Title

    * Permit restricted form of equality

       - Further discussion - Put into RIFRAF

No Title

    * Tagging intended semantics

       - See previous

No Title

    * Higher order and frame based syntax

    * Two requirements, moved to RIFRAF

No Title

    * Consistency with major market technologies

    * Too vague, replaced with:

       - RIF should accept Relational Tables/Views as data. (move to
         data sources e.g. RDF, XML, ...) 

       - Permit SQL queries to be used in rules. (moved to data sources)

       - RIF should accept UML Instances as data. (??? future discussion)

       - RIF should accept ORM Fact Model populations as data. (???
         future discussion) 

       - RIF should express SBVR business rules (moved to RIFRAF)

No Title

    * Meta-data for currency of rules

       - RIF will have a notion of when rules apply.

       - IsnÇt this just a condition on a rule?

       - Possibly discuss later with meta-data like author

No Title

    * Capability to pass descriptive text through RIF

    * RIF shoudl be able to pass comments

    [[ Phase 1 ]]

No Title

    * Meta-data indicating executability of rules

    * Needs further discussion

No Title

    * RIF scope -- exchange of RDFS/OWL fact models

    * Add to RDF/OWL data-source discussion

No Title

    * Four modal operators

    * Goes to RIFRAF

================================================================

[1] http://lists.w3.org/Archives/Public/public-rif-wg/2006Jun/0097
[2] My conversion path was to load the powerpoint slides in openoffice
    then save as xhtml, then load the xhtml in firefox and cut/paste
    into emacs.  I had to do some search/replace cleanup on both the
    xhtml and plain-text versions.
Received on Saturday, 10 June 2006 13:04:23 GMT

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