What is a name variant ?
Database applications that involve the storing and searching for personal data often need to allow for a degree of variation in the spelling of both surnames and forenames.

Variations can be introduced into database applications as a result of typographical errors where letters are interchanged (e.g. Nobel and Noble), letters are substituted (e.g. Stevens and Stephens), letters are added (e.g. Colins and Collins) or removed (e.g. Clarke and Clark).

Variations can also be introduced as a result of alternate spelling for names with the same or very similar pronunciation (e.g. Cavenagh and Kavenagh or Ewal and Yule or Sean and Shawn). This is a particular problem where the transcription is from the spoken word. 

Forename abbreviations introduce further problems and in many cases there is little or no phonetic link (e.g. William with Wm,Billy,Bill,etc or Elizabeth with Lizzie,E'beth,Elz,Beth,etc).

In addition, we do not want to match known masculine names with known feminine variants and vice versa (e.g. Alexander should match with Alex and Alexandar but not with Alexandria.
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Why do we need another name matching system ?
Many techniques have been used to assist with the important problem of matching variant names. However, most of these techniques were developed for general word matching and as a result they are not optimised for name matching. The NameThesaurus was designed specifically for name matching and achieves significantly higher precision with higher recall than the alternatives.
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What is wrong with Soundex and Metaphone ?
Soundex is a simple algorithm that transforms any word into a code comprising a leading letter followed by up to three digits. For example, Kavenagh gets the code K152 and this may be matched to other names with the same code such as Kavnaugh and Kavenough. Unfortunately the same code also matches with a huge number of unrelated names such as Kyppins and Koppensteiner. This code also fails to match any name with a different leading letter such as Cavenagh. In summary Soundex offers a reasonable level of recall but with low precision when matching names.

Neither Soundex nor Metaphone include any of the following matches for Kavenagh: Kavena, Cavena, Kavanha, Kavan.  Also, neither algorithm offers any assistance with the problem of forename abbreviations.
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What algorithms does the NameThesaurus use ?
The NameThesaurus uses a combination of phonetic and other techniques for name variant identification.

All surnames are limited to 27 characters (a-z and " ' "). Double-barrelled names are split into their component parts and treated independently. All accented characters are converted to their closest matching letter (e.g. à, â, ä and å are all mapped to " a "). This mapping is used to simplify the thesaurus and ensures that similar names are located without regard to the use of accented characters.

Once a potential match has been identified a weighting is computed as follows:

1.	All surnames are converted to a phonetic encoding.
2.	The degree of similarity for potential matches are computed using two different matching algorithms. Both the original and the phonetic versions are compared using the two matching algorithms producing a total of four match scores.
3.	The Soundex and Metaphone codes are also computed.
4.	The Match Score is computed from the weighted average of the four match scores combined with the results of the Soundex and Metaphone encodings.
5.	For forenames, the NameThesaurus uses a knowledge of gender associations so that close phonetic matches between the sexes can be avoided (e.g. John and Joan or Alexander and Alexandria).

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Why are weighted pairs important ?
Neither Soundex nor Metaphone is able to rank their matching names so that the closer matches can be identified. Therefore an application that uses these techniques has an all-or-nothing decision regarding the inclusion of name variants.

By assigning a weight to each name variant the application has the option of limiting a particular search to the better matches thus improving precision at the expense of recall.
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What do you mean by Precision and Recall ?
Precision measures the percentage of correct names in a match list with 100% indicating that the match list does not contain any invalid names.

In all cases the NameThesaurus provides better Precision than either Soundex or Metaphone.
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How do I work with the NameThesaurus ?
The NameThesaurus data is organised as a thesaurus of name pairs with weights and would normally be held in a relational database. Database applications that wish to utilise the NameThesaurus would simply include a sub-select to include matching names from the Thesaurus above the selected threshold.
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Is the NameThesaurus just data ? 
Yes - the NameThesaurus is available as a standard thesaurus containing 233 million variants for 4.3 million distinct Surnames and 21 million variants for 1.1 million distinct Forenames.

The names in the standard thesaurus come from all over the world.
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Is the NameThesaurus a Thesaurus generation Service ? 
Yes - we can build custom thesauri for specific name collections. 
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How fast is the NameThesaurus ? 
The performance of the NameThesaurus is dependent upon the speed of the relational database used to hold the Thesauri. Since the sub-select can easily be controlled by a clustered index the overhead of fetching the additional variants is normally a small percentage of the overall search time. Our customers use the NameThesaurus with databases that hold hundreds of millions of name.  
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Who are Image Partners ?
Image Partners Limited is the company that designed and developed the NameThesaurus.

John Challis, who founded the company in 1996, has been designing software products for the management of unstructured information since 1987.
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