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<filter expression> Specifics:

 A A logical expression used to select datasets that meet specific criteria.  Here's a loose grammar which defines expressions:

Expr ::= Expr
Expr ::= '(' Expr ')'
Expr ::= '!' Expr
Expr ::= Expr LogOp Expr
LogOp ::= '&&' | '||'
Expr ::= Comparable CmpOp Comparable
CmpOp ::= '==' | '!=' | '>=' | '<='
Comparable ::= "String"                -- a String constant must be enclosed in double quotes
Comparable ::= Number
Comparable ::= Identifier
Comparable ::= UnOp Comparable
UnOp ::= '-' | '+'
Comparable ::= Comparable BinOp Comparable
BinOp ::= '/' | '*' | '+' | '-'

Examples: