* * It has evolved out of the first-cut grammar for a minimal * "human-readable" syntax, which is described in the proposal * submitted to the W3C Working Group on the Rule Interchange Format * (RIF) by Harold Boley et al., on April 23, 2006. It is meant * to be able to express the abstract syntax form taken by * conditions of the rules that appear to be common to a * reasonably large variety of families of rule languages. The proposal * in question is available from the public RIF WG mail archive: * [RIF] Extensible Design. * *
* * This Jacc grammar specification is a literal transcription of the BNF * rules given in the above references. * *
* * This version of the HRL (and RCL) grammar(s) is annotated for simple * XML serialization using namespace labells identifying the language * level at which the constructs belong. * *
* * We give below the Jacc grammar rules for a "full" HRL using the a * version "full" RCL. We use Jacc's %include commands to make * the grammars modular. Note that the full HRL grammar that is the * combination of all the partial included grammars defines a LALR(1) * grammar. Thus, so are simpler grammars using a less full version of * the RCL (or HRL) - i.e., by including less rules. * *
* * This HTML file is the root of a hyperlinked documentation allowing * one to explore the grammar via navigation through its elements - * rules, terminal and non-terminal symbols. The comments accompanying * some rules come from the original documents. It also contains the * pure Yacc rules. This documentation is generated by Jacc from the * Jacc grammar specified in file HRL.grm (i.e., with the command * "jacc -doc HRL"). Along with this Jacc grammar file, there are * other supporting source files. * *
* * Essentially, the rule format is that of Yacc. As in Yacc, Jacc rules may * be annotated with semantic actions, in the form of code involving the * rule's RHS constituents (denoted by $1, $2, * ..., $n - the so-called pseudo-variables where the index * n in $n refers to the order of RHS * constituents. Such actions appear between curly braces ('{' and * '}') wherever a symbol may appear in a rule's RHS. * * Jacc also allows an additional form of annotation in the RHS of a rule * to indicate the XML serialization pattern of the abstract syntactic * tree (AST) node corresponding to a derivation with this rule. This XML * serialization meta-annotation comes between square brackets * ('[' and ']') and is of the form: * *
* [ XmlTag n_1 ... n_k ] ** * where
XmlTag is an identifier to use as XML tag for this
* node in the XML serialization of the AST, and the n_k's
* are a sequence of numbers denoting positions of symbols in the RHS of
* the rule (as for pseudo-variables but without '$'). The
* number sequence indicates the order in which subnodes are to be
* serialized. For example, the annotated rule:
*
*
* QUANTIF
* : 'Exists' Var_plus '(' CONDIT ')'
* [ Exists 2 4 ]
* ;
*
*
* means that an AST node for this rule will be serialized thus:
*
* * <Exists> * (Xml serialization of Var_plus) * (Xml serialization of CONDIT) * </Exists> ** * Rules without XML serialization annotation follow a default behavior: * the serialization is the concatenation of those of its RHS's * constituents, eliminating punctuation tokens (i.e., empty nodes * and literal tokens - namely, tokens that do not carry a value). * *
* * For example, see the two test files Test.hrl and Test2.hrl. Running the * command hrl on them produces * the outputs shown in Test.xml and Test2.xml. */ //////////////////////////////////////////////////////////////////////// %package ilog.rif; %include Keywords.grm // RCL language reserved keywords %include ParserCode.grm // Code for setting params and showing xml serialization %token Name Fun Rel Value Var // NB: Var is a token (i.e., the '?' is part of it) %xmlns "rif" "http://www.w3.org/2007/rif#" %start ROOT //////////////////////////////////////////////////////////////////////// %% /** * Horn Rule Language (HRL) program grammar's root. */ ROOT : HRL { showXml(); } // show the XML tree ; /** * HRL program units are mae of declarations and rulesets. */ HRL : RuleSet [ rif:RuleSet 1 ] // XML serialization pattern ; /** * Rulesets are sequences of ruleset items. */ RuleSet : RuleSetItem | RuleSet RuleSetItem ; /** * A RuleSetItem is a declaration or a rule. */ RuleSetItem : Declaration ';' | Rule ; /** * Declarations are needed to discriminate relation and function symbols. * NB: an identifier can be declared explicitly as either a relation symbol * or a function symbol. An undeclared identifier will cause an error. */ Declaration : 'Relation' Name { Lexicon.relation($2.svalue()); } // make this a relation's name [ rif:Relation 2 ] // XML serialization pattern | 'Function' Name { Lexicon.function($2.svalue()); } // make this a function's name [ rif:Function 2 ] // XML serialization pattern ; /** * A Horn rule is a kind of rule. */ Rule : HornRule [ rif:HornRule 1 ] // XML serialization pattern ; /** * A Horn rule is a logical implication. */ HornRule : Implication ; /** * An implication consists of a $HEAD$ (the LHS - what's on the left of * $:-$) and a $BODY$ (the RHS - what's on the right of $:-$). */ Implication : HEAD ':-' BODY [ hrl:Implies 3 1 ] // XML serialization pattern ; /** * A Horn rule's head is a literal formula ($LITFORM$). */ HEAD : LITFORM [ hrl:Consequent 1 ] // XML serialization pattern ; /** * A Horn rule's body is a condition ($CONDIT$). */ BODY : CONDIT [ hrl:Antecedent 1 ] // XML serialization pattern ; //////////////////////////////////////////////////////////////////////// // Includes: //////////////////////////////////////////////////////////////////////// // RIF Condition Language basis: %include RCL_basis.grm // RCL's dual (value,object) constants: %include RCL_valobj.grm // RCL's universal quantification: %include RCL_forall.grm // RCL's constructive negation: %include RCL_neg.grm // RCL's negation-as-failure: %include RCL_naf.grm // RCL's both negation-as-failure and constructive negation: %include RCL_nafneg.grm %% ////////////////////////////////////////////////////////////////////////