Class ColognePhonetic

Encodes a string into a Cologne Phonetic value.

Inheritance

System.Object

ColognePhonetic

Implements

IStringEncoder

Inherited Members

System.Object.Equals(System.Object)

System.Object.Equals(System.Object, System.Object)

System.Object.GetHashCode()

System.Object.GetType()

System.Object.MemberwiseClone()

System.Object.ReferenceEquals(System.Object, System.Object)

System.Object.ToString()

Namespace: Lucene.Net.Analysis.Phonetic.Language

Assembly: Lucene.Net.Analysis.Phonetic.dll

Syntax

public class ColognePhonetic : IStringEncoder

Remarks

Implements the KÖlner Phonetik (Cologne Phonetic) algorithm issued by Hans Joachim Postel in 1969.

The KÖlner Phonetik is a phonetic algorithm which is optimized for the German language. It is related to the well-known soundex algorithm.

Algorithm

• Step 1: After preprocessing (conversion to upper case, transcription of germanic umlauts, removal of non alphabetical characters) the letters of the supplied text are replaced by their phonetic code according to the following table.

  Letter	Context	Code
  A, E, I, J, O, U, Y		0
  H		-
  B		1
  P	not before H	1
  D, T	not before C, S, Z	2
  F, V, W		3
  P	before H	3
  G, K, Q		4
  C	t onset before A, H, K, L, O, Q, R, U, X OR before A, H, K, O, Q, U, X except after S, Z	4
  X	not after C, K, Q	48
  L		5
  M, N		6
  R		7
  S, Z		8
  C	after S, Z OR at onset except before A, H, K, L, O, Q, R, U, X OR not before A, H, K, O, Q, U, X	8
  D, T	before C, S, Z	8
  X	after C, K, Q	8

  (Source: Wikipedia (de): KÖlner Phonetik -- Buchstabencodes)

  Example:

  "MÜller-LÜdenscheidt" => "MULLERLUDENSCHEIDT" => "6005507500206880022"
• Step 2: Collapse of all multiple consecutive code digits.

  Example:

  "6005507500206880022" => "6050750206802"
• Step 3: Removal of all codes "0" except at the beginning. This means that two or more identical consecutive digits can occur if they occur after removing the "0" digits.

  Example:

  "6050750206802" => "65752682"

This class is thread-safe.

See: Wikipedia (de): Kölner Phonetik (in German)

since 1.5

Methods

Encode(String)

Declaration

public virtual string Encode(string text)

Parameters

Type	Name	Description
System.String	text

Returns

Type	Description
System.String

GetColognePhonetic(String)

Implements the Kölner Phonetik algorithm.

In contrast to the initial description of the algorithm, this implementation does the encoding in one pass.

Declaration

public virtual string GetColognePhonetic(string text)

Parameters

Type	Name	Description
System.String	text

Returns

Type	Description
System.String	The corresponding encoding according to the Kölner Phonetik algorithm

IsEncodeEqual(String, String)

Declaration

public virtual bool IsEncodeEqual(string text1, string text2)

Parameters

Type	Name	Description
System.String	text1
System.String	text2

Returns

Type	Description
System.Boolean

Implements

IStringEncoder