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.

• 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

• 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

• 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

• 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

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

• removed

• 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

• 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

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

• Replaced by RIF must be implementable...

• 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

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

• RIF should be implementable using well understood implementation techniques

• Phase I

• 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

• 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

• 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 • 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

• RIF should express RDF deduction rules– RIF shoudl cover RDF deduction rules

(agreement)– Should be a RIFRAF classification– Phasing TBD as part of RIFRAF

• Permit SPARQL queries to be used in rules– Pointer to previous req.– Covered by external call– Phase 2, but...

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?)

• RIF will cover the set of languages identified in RIFRAF– We will use RIFRAF to identify classes of

languages to be covered by RIF

• 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

• 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

• Permit restricted form of equality– Further discussion - Put into RIFRAF

• Tagging intended semantics– See previous

• Higher order and frame based syntax

• Two requirements, moved to RIFRAF

• 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)

• Meta-data for currency of rules– RIF will have a notion of when rules apply.– Isn’t this just a condition on a rule?– Possibly discuss later with meta-data like

author

• Capability to pass descriptive text through RIF

• RIF shoudl be able to pass comments

• Meta-data indicating executability of rules

• Needs further discussion

• RIF scope – exchange of RDFS/OWL fact models

• Add to RDF/OWL data-source discussion

• Four modal operators

• Goes to RIFRAF