From: Harold Boley (boley@informatik.uni-kl.de)
Date: 09/02/03
CONCRETE SYNTAX FOR RULES LITE Draft 2 Sept 2003 Harold Boley and Said Tabet This is an update to the Rules Lite concrete syntax work on Datalog facts, rules, and queries (also usable as 'positive' or 'negative' integrity constraints). In the following examples all predicates will be unary or binary (compatible with OWL-DL) or ternary (demonstrating the extension path to N-ary relations). The unary predicates could also be employed for typing some of the rule variables (the others being of type 'any'), as discussed in an earlier series of JC telecons (http://www.daml.org/listarchive/joint-committee/1230.html). By allowing OWL's allValuesFrom and someValuesFrom restrictions (http://www.w3.org/TR/owl-guide/#allValuesFrom) in Rules Lite's bodies and (perhaps) heads, the concrete syntax could be further adapted to the recent OWL Rules proposal: http://www.daml.org/listarchive/joint-committee/1430.html A new Abridged RuleML/XML is presented here that also permits infix operators (even for N-ary relations): *1* The earlier <_opr><rel>relation</rel></_opr> will be abridged to <_opr>relation</_opr>. *2* The earlier <_body><and>atom1...atomK</and></_body> will be abridged to <_body>atom1...atomK</_body>. *3* Similarly, <_head><and>atom1...atomK</and></_head> could be abridged to <_head>atom1...atomK</_head> (for OWL Rules). *4* Besides <atom><_opr>relation</_opr>term1...termN</atom> and <atom>term1...termN<_opr>relation</_opr></atom>, also <atom>term1<_opr>relation</_opr>term2...termN</atom> and all other infix uses of _opr will be allowed. While this is a concrete XML syntax, it builds on a data model integrating the data models of XML and RDF: A role like _opr corresponds to an RDF property (used as an arc label in its DLG model). Allowing infix operators does not change this data model, so the abstract syntax for all concrete syntax variations in *4* is the 'atom'-rooted tree with an operator and a sequence of the N argument terms as subtrees. Prolog examples will be followed by Abridged RuleML/XML syntax: * Prolog: Always uses prefix operators. * XML: Uses Abridged RuleML/XML syntax as proposed in http://www.daml.org/listarchive/joint-committee/1411.html, but now also permits infix operators as prepared in http://www.daml.org/listarchive/joint-committee/1427.html. Facts ----- Prolog: continent(North_America). ocean(Atlantic). ocean(Pacific). has_as_part(North_America,Canada). has_as_part(Canada,Ontario). between(North_America,Atlantic,Pacific). XML (prefix, postfix, and infix operators): <rulebase> <fact> <_head> <atom> <_opr>continent</_opr> <ind>North America</ind> </atom> </_head> </fact> <fact> <_head> <atom> <ind>Atlantic</ind> <_opr>ocean</_opr> </atom> </_head> </fact> <fact> <_head> <atom> <ind>Pacific</ind> <_opr>ocean</_opr> </atom> </_head> </fact> <fact> <_head> <atom> <ind>North America</ind> <_opr>has as part</_opr> <ind>Canada</ind> </atom> </_head> </fact> <fact> <_head> <atom> <ind>Canada</ind> <_opr>has as part</_opr> <ind>Ontario</ind> </atom> </_head> </fact> <fact> <_head> <atom> <ind>North America</ind> <_opr>between</_opr> <ind>Atlantic</ind> <ind>Pacific</ind> </atom> </_head> </fact> </rulebase> Rules ----- Prolog (to be executed with iterative deepening): has_as_part(x,z) :- has_as_part(x,y), has_as_part(y,z). between(x,y,z) :- between(x,z,y). XML (infix operators): <rulebase> <imp> <_head> <atom> <var>x</var> <_opr>has as part</_opr> <var>z</var> </atom> </_head> <_body> <atom> <var>x</var> <_opr>has as part</_opr> <var>y</var> </atom> <atom> <var>y</var> <_opr>has as part</_opr> <var>z</var> </atom> </_body> </imp> <imp> <_head> <atom> <var>x</var> <_opr>between</_opr> <var>y</var> <var>z</var> </atom> </_head> <_body> <atom> <var>x</var> <_opr>between</_opr> <var>z</var> <var>y</var> </atom> </_body> </imp> </rulebase> Conjunctive Queries (as 'Negative' Integrity Constraints) ------------------------------------------------------- Prolog: continent(x), ocean(x). XML (prefix and postfix operators): <query> <_body> <atom> <_opr>continent</_opr> <var>x</var> </atom> <atom> <var>x</var> <_opr>ocean</_opr> </atom> </_body> </query> Least Herbrand Models (as Ground Facts) --------------------------------------- Prolog: continent(North_America). ocean(Atlantic). ocean(Pacific). has_as_part(North_America,Canada). has_as_part(Canada,Ontario). has_as_part(North_America,Ontario). between(North_America,Atlantic,Pacific). between(North_America,Pacific,Atlantic). XML (prefix operators): <rulebase> <fact> <_head> <atom> <_opr>continent</_opr> <ind>North America</ind> </atom> </_head> </fact> <fact> <_head> <atom> <_opr>ocean</_opr> <ind>Atlantic</ind> </atom> </_head> </fact> <fact> <_head> <atom> <_opr>ocean</_opr> <ind>Pacific</ind> </atom> </_head> </fact> <fact> <_head> <atom> <_opr>has as part</_opr> <ind>North America</ind> <ind>Canada</ind> </atom> </_head> </fact> <fact> <_head> <atom> <_opr>has as part</_opr> <ind>Canada</ind> <ind>Ontario</ind> </atom> </_head> </fact> <fact> <_head> <atom> <_opr>has as part</_opr> <ind>North America</ind> <ind>Ontario</ind> </atom> </_head> </fact> <fact> <_head> <atom> <_opr>between</_opr> <ind>North America</ind> <ind>Atlantic</ind> <ind>Pacific</ind> </atom> </_head> </fact> <fact> <_head> <atom> <_opr>between</_opr> <ind>North America</ind> <ind>Pacific</ind> <ind>Atlantic</ind> </atom> </_head> </fact> </rulebase>
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