This is the Baseline module of FLD. It is the foundation of the full schema defined through the Skyline module. The Baseline XML schema is based on the following EBNF (compared to the full EBNF of RIF-FLD, Group and Document are omitted, and 'Implies' is missing from the productions for FORMULA and TERMULA). The nonterminals starting with NEW provide extensions points for FLD (cf. Section 4 XML Serialization Framework). FORMULA ::= IRIMETA? CONNECTIVE '(' FORMULA* ')' | IRIMETA? QUANTIFIER '(' FORMULA ')' | IRIMETA? 'Neg' FORMULA | IRIMETA? 'Naf' FORMULA | IRIMETA? FORMULA '@' MODULEREF | FORM FORM ::= IRIMETA? (Var | ATOMIC | 'External' '(' ATOMIC LOCATOR? ')') ATOMIC ::= Const | Atom | Equal | Member | Subclass | Frame Atom ::= UNITERM UNITERM ::= TERMULA '(' (TERMULA* | (Name '->' TERMULA)*) ')' Equal ::= TERMULA '=' TERMULA Member ::= TERMULA '#' TERMULA Subclass ::= TERMULA '##' TERMULA Frame ::= TERMULA '[' (TERMULA '->' TERMULA)* ']' TERMULA ::= IRIMETA? CONNECTIVE '(' TERMULA* ')' | IRIMETA? QUANTIFIER '(' TERMULA ')' | IRIMETA? 'Neg' TERMULA | IRIMETA? 'Naf' TERMULA | IRIMETA? TERMULA '@' MODULEREF | TERM TERM ::= IRIMETA? (Var | EXPRIC | List | 'External' '(' EXPRIC LOCATOR? ')' | AGGREGATE | NEWTERM) EXPRIC ::= Const | Expr | Equal | Member | Subclass | Frame Expr ::= UNITERM List ::= 'List' '(' TERM* ')' | 'List' '(' TERM+ '|' TERM ')' AGGREGATE ::= AGGRFUNC '{' Var ('[' Var+ ']')? '|' FORMULA '}' Const ::= '"' UNICODESTRING '"^^' SYMSPACE | CONSTSHORT MODULEREF ::= Var | Const | Expr CONNECTIVE ::= 'And' | 'Or' | NEWCONNECTIVE QUANTIFIER ::= ('Exists' | 'Forall' | NEWQUANTIFIER) Var* AGGRFUNC ::= 'Min' | 'Max' | 'Sum' | 'Prod' | 'Avg' | 'Count' | 'Set' | 'Bag' | NEWAGGRFUNC SYMSPACE ::= ANGLEBRACKIRI | CURIE LOCATOR ::= ANGLEBRACKIRI Var ::= '?' Name Name ::= NCName | '"' UNICODESTRING '"' IRIMETA ::= '(*' Const? (Frame | 'And' '(' Frame* ')')? '*)'