org.knime.base.node.rules
Class Rule

java.lang.Object
  org.knime.base.node.rules.Rule

public class Rule
extends Object

A rule consists of a condition part (antecedant) and an outcome (consequent). The condition may consists of arithmetic or string comparisons combined by boolean operators. The outcome is a simple string. The grammar for a rule is as follow:

 RULE := BEXPR '=>' STRING | NUMBER | COL
 BEXPR := '(' BEXPR ')' |
          'NOT' BEXPR |
          'MISSING' COL |
          AEXPR (BINOP BEXPR)?
 AEXPR := COL OP COL |
          NUMBER OP COL |
          COL OP NUMBER |
          STRING OP COL |
          COL OP STRING |
          COL LOP STRINGLIST
 BOP := 'AND' | 'OR' | 'XOR'
 OP := '>' | '<' | '>=' | '<=' | '=' | 'LIKE'
 LOP := 'IN'
 STRING := '"' [ˆ"]* '"'
 NUMBER := [1-9][0-9]*(\.[0-9]+)?
 COL := '$' [ˆ$]+ '$'
 STRINGLIST := '(' STRING (',' STRING)* ')'
 

The operators should be self-describing, if not look them up in SQL ;-)
While parsing a rule, the parser also checks if the arithmetic operations are in fact done with numerical columns and throws an exception if not. Therefore the constructor needs the spec of the table on which the rule will lateron be used.

Author:

Thorsten Meinl, University of Konstanz

Nested Class Summary

(package private) static class	Rule.ColumnReference
static class	Rule.Operators Enumeration for all possible operators used in a rule.

Constructor Summary

Rule(String rule, DataTableSpec spec)
Creates a new rule by parsing a rule string.

Method Summary

String	getCondition() Returns the rule's condition (antecedant).
Object	getOutcome() Returns the rule's outcome (consequent).
static void	main(String[] args) Zum Testen...
boolean	matches(DataRow row) Returns if this rules matches the given row.
String	serialize() Returns the parsed rule in string representation.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Rule

public Rule(String rule,
            DataTableSpec spec)
     throws ParseException

Creates a new rule by parsing a rule string.

Parameters:

rule - the rule string

spec - the spec of the table on which the rule will be applied.

Throws:

ParseException - if the rule contains a syntax error

Method Detail

matches

public boolean matches(DataRow row)

Returns if this rules matches the given row.

Parameters:

row - a data row

Returns:

true if the rule matches, false otherwise

getOutcome

public Object getOutcome()

Returns the rule's outcome (consequent).

Returns:

a string

getCondition

public String getCondition()

Returns the rule's condition (antecedant).

Returns:

the condition

toString

public String toString()

Overrides:

toString in class Object

serialize

public String serialize()

Returns the parsed rule in string representation. This representation is not completely identical to the input rule string, but the logical structure should match.

Returns:

a string representation of this rule

main

public static void main(String[] args)
                 throws Exception

Zum Testen...

Parameters:

args - Pieps

Throws:

Exception - Tröt