Main Documentation for grammar BLD.grm

This is a Jacc grammar for the so-called presentation syntax of the RIF Basic Logic Dialext (BLD) developed as a result of the activities of the RIF Working Group (Phase 1).

Specific relevant sections in the RIF WG reference documents RIF Basic Logic Dialect (BLD):

• EBNF for the BLD Condition Language
• EBNF for the BLD Rule Language
• Translation rules for BLD XML Serialization

This Jacc grammar specification given here is a literal transcription of the BNF rules given in the above references. There are two sets of grammar rules:

1. the rules for the Basic Logic Condition (BLC) language; and,
2. the rules for the Basic Logic Rule language (BLR).

These two grammars expressed in Yacc form are:

1. BLD Condition Language

     Formula
       : Atomic
       | AND OPENPAR Formulas_opt CLOSEPAR
       | OR OPENPAR Formulas_opt CLOSEPAR
       | EXISTS Vars OPENPAR Formula CLOSEPAR
       | EXTERNAL OPENPAR Atom CLOSEPAR
       ;
     
     Atomic
       : Atom
       | Equal
       | Member
       | Subclass
       | Frame
       ;
     
     Atom
       : UniTerm
       ;
     
     UniTerm
       : Const OPENPAR UniTermBody CLOSEPAR
       ;
     
     Equal
       : Term EQUAL Term
       ;
     
     Member
       : Term MEMBER Term
       ;
     
     Subclass
       : Term SUBCLASS Term
       ;
     
     Frame
       : Term OPENBRA FrameAttributes_opt CLOSEBRA
       ;
     
     Term
       : Const
       | Var
       | Expr
       | EXTERNAL OPENPAR Expr CLOSEPAR
       ;
     
     Expr
       : UniTerm
       ;
     
     Const
       : STRING LEXSPACE SymSpace
       ;
     
     Var
       : VARIABLE
       ;
     
     UniTermBody
       : Terms_opt
       | TermAttributes_opt
       ;
     
     TermAttributes_opt
       : // empty
       | TermAttributes
       ;
     
     TermAttributes
       : TermAttribute
       | TermAttributes TermAttribute
       ;
     
     TermAttribute
       : Const ARROW Term
       ;
     
     FrameAttributes_opt  
       : // empty
       | FrameAttributes
       ;
     
     FrameAttributes
       : FrameAttribute
       | FrameAttributes FrameAttribute
       ;
     
     FrameAttribute
       : Term ARROW Term
       ;
     
     Formulas_opt
       : // empty
       | Formulas
       ;
     
     Formulas
       : Formula
       | Formulas Formulas
       ;
     
     Terms_opt
       : // empty
       | Terms_opt Term
       ;
     
     Vars
       : Var
       | Vars Var
       ;
     
     SymSpace
       : IDENTIFIER COLON IDENTIFIER
       ;  
     
     

2. BLD Rule Language

     Group
       : GROUP Meta_opt OPENPAR RuleSet_opt CLOSEPAR
       ;
     
     Meta
       : Frame
       ;
     
     Rule
       : Clause
       | FORALL Vars_opt OPENPAR Clause CLOSEPAR
       ;
     
     Clause
       : Atomic
       | Implies
       ;
     
     Implies
       : Atomic IF Formula
       ;
     
     RuleSet_opt
       : // empty
       | RuleSet
       ;
     
     RuleSet
       : RuleOrGroup
       | RuleSet RuleOrGroup
       ;
    
     RuleOrGroup
       : Rule
       | Group
       ;
    
     Meta_opt
       : // empty
       | Meta
       ;
     
     Vars_opt
       : // empty
       | Vars
       ;
     

This version of the BLD grammar is annotated for simple XML serialization as per the scheme specified in the current BLD document. If and where we may diverge with what is the BLD document, it will be indicated in what mannner and why.

This HTML file is the root of a hyperlinked documentation allowing one to explore the Jacc grammar for BLD 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 - i.e., without semantic actions. This documentation is generated by Jacc from the Jacc grammar specified in file BLD.grm (i.e., with the command "jacc -doc BLD"). Along with this Jacc grammar file, there are other supporting source files.

Essentially, the format of a Jacc grammar is that of a Yacc grammar. As in Yacc, Jacc rules may be annotated with semantic actions in the form of Java 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 described by this Jacc grammar for a XML annotation language for a Jacc grammar! (Yes - it generates a a meta-metaparser.)

For example, the annotated rule:

  QUANTIF
     : 'Exists' Var_plus '(' CONDIT ')'
     [
         nsprefix   : hrl
         localname  : quantifier
         attributes : {kind="existential"}
         children   : (2,4)
     ]
     ;
  

   <hrl:quantifier kind="existential">
     (XML serialization of Var_plus)
     (XML serialization of CONDIT)
   </hrl:quantifier>
  

For example, see the two test files test1.bld and test2.bld. Running the command bld on them produces the XML trees shown in test1.xml and test2.xml.

The terminal symbols are:

Important Notes:

• VARIABLE is a token recognized thanks to its leading '?' but the token returned by the lexer suppresses this leading '?'. This means that '?' is not a separate punctuation mark as shown by the EBNF.

• Using STRING dispenses from the spurious "..."^^ notation, making '^^' an infix operator. In other words, the initial and final double quotes are part of the token itself an need not appear at the grammar level.

• IDENTIFIER is any maximal sequence of non-separator not-punctuation unicode characters that does not start with a '?'.

• For now, a SymSpace is simply parsed as a pair of IDENTIFIERs separated by a colon (':'). This means that ':' is a separate punctuation mark unlike what is shown by the EBNF.