Phonetic Algorithm: Bryan, Brian, Briane, Bryne, or … what was his name again?

Let the spelling loose …

What do Callie and Kelly have in common (except for the double ‘l’ in the middle)? What about “no” and “know”, or “Ceasar’s” and “scissors” and what about “message” and “massage”? You definitely got it – Callie and Kelly, “no” and “know”, “Ceasar’s” and “scissors” sound alike, but are spelled quite differently. “message” and “massage” on the other hand differ by only one vowel (“a” vs “e”) but their pronunciation is not at all the same.

It’s a well known fact for many languages that ortography does not determine the pronunciation of words. English is a classic example. George Bernard Shaw was the attributed author of “ghoti” as an alternative spelling of “fish”. And while phonology often reflects the current state of the development of the language, orthography may often lag centuries behind. And while English is notorious for that phenomenon it is not the only one. Swedish, French, Portuguese, among others, all have their ortography/pronunciation discrepancies.

Phonetic Algorithms

So how do we represent things that sound similar but are spelled different? It’s not trivial but for most cases it is not impossible either. Soundex is probably the first algorithm to tackle this problem. It is an example of the so called phonetic algorithms which attempt to solve the problem of giving the same encoding to strings which are pronounced in a similar fashion. Soundex was designed for English only but has its limits. DoubleMetaphone (DM) is one of the possible replacements and relatively successful. Designed by Lawrence Philips in the beginning of 1990s it not only deals with native English names but also takes proper care of foreign names so omnipresent in the language. And what is more – it can output two possible encodings for a given name, hence the “Double” in the naming of the algorithm, – an anglicised and a native (be that Slavic, Germanic, Greek, Spanish, etc.) version.

By relying on DM one can encode all the four names in the title of this post as “PRN”. The name George will get two encodings – JRJ and KRK, the second version reflecting a possible German pronunciation of the name. And a name with Polish origin, like Adamowicz, would also get two encodings – ATMTS and ATMFX, depending on whether you pronounce the “cz” as the English “ch” in “church” or “ts” in “hats”.

The original implementation by Lawrence Philips allowed a string to be encoded only with 4 characters. However, in most subsequent
implementations of the algorithm this option is parameterized or just omitted.

Apache Commons Codec has an implementation of the DM among others (Soundex, Metaphone, RefinedSoundex, ColognePhonetic, Coverphone, to
name just a few.) and here is a tiny example with it:

import org.apache.commons.codec.language.DoubleMetaphone;

public class DM {

public static void main(String[] args) {

String s = "Adamowicz";

DoubleMetaphone dm = new DoubleMetaphone();

// Default encoding length is 4!

// Let's make it 10


System.out.println("Alternative 1: " + dm.doubleMetaphone(s) +

// Remember, DM can output 2 possible encodings:

"nAlternative 2: " + dm.doubleMetaphone(s, true));


The above code will print out:

Alternative 1: ATMTS

Alternative 2: ATMFX

It is also relatively straightforward to do phonetic search with Solr. You just need to ensure that you add the phonetic analysis to a field which contains names in your schema.xml:


While DM does perform quite well, at first sight, it has its limitations. We should know that it still originated from the English language and although it aims to tackle a variety of non-native borrowings most of the rules are English-centric. Suppose you work on any of the Scandinavian languages (Swedish, Danish, Norwegian, Icelandic) and one of the names you want to encode is “Örjan”. However, “Orjan” and “Örjan” get different encodings – ARJN vs RJN. Why is that? One look under the hood (the implementation in will give you the answer:

private static final String VOWELS = "AEIOUY";

So the Scandinavian vowels “ö”, “ä”, “å”, “ø” and “æ” are not present. If we just add these then compile and use the new version of the DM implementation we get the desired output – ARJN for both “Örjan” and “Orjan”.

Finally, if you don’t want to use DM or maybe it is really not suitable for your task, you still may use the same principles and create your own encoder by relying on regular expressions for example. Suppose you have a list of bogus product names which are just (mis)spelling variations of some well known names and you want to search for the original name but get back all ludicrous variants. Here is one albeit very naïve way to do it. Given the following names:








and with a bunch of regular expressions you can easily encode them as “cphldR” and “mclnR”.

String[] ar = new String[]{"CupHoulder", "CappHolder", "KeepHolder",
"MacKleena", "MackCliiner", "MacqQleanAR", "Ma'cKcle'an'ar"};

for (String a : ar) {
a = a.toLowerCase();
a = a.replaceAll("[ae]r?$", "R");
a = a.replaceAll("[aeoiuy']", "");
a = a.replaceAll("pp+", "p");
a = a.replaceAll("q|k", "c");
a = a.replaceAll("cc+", "c");

You can now easily find all the ludicrous spellings of “CupHolder” och “MacCleaner”.

I hope this blogpost gave you some ideas of how you can use phonetic algorithms and their principles in order to better discover names and entities that sound alike but are spelled unlike. At Findwise we have done a number of enhancements to DM in order to make it work better with Swedish, Danish and Norwegian.


You can learn more about Double Metaphone from the following article by the creator of the algorithm:

A German phonetic algorithm is the Kölner Phonetik:ölner_Phonetik

And SfinxBis is a phonetic algorithm based on Soundex and is Swedish specific:

How to Index and Search XML Content in Solr

Indexing XML Content

In solr, there is an xml update request handler which can be used to update xml formatted data.

For example,

<field name="employeeId">05991</field>
<field name="office">Bridgewater</field>
<field name="skills">Perl</field>
<field name="skills">Java</field>
[<doc> ... </doc>[<doc> ... </doc>]]

However when a field itself should contain xml formatted data, the xml update handler will fail to import. Because, xml update handler parse the import data with xml parser, it will try to get direct child text under ‘field’ node, which is empty if a field’s direct child is xml tag.

What we can do is to use json update handler. For example:

    "id" : "MyTestDocument",
    "title" : "<root p="cc">test \ node</root>"

There are two things to notice,

  1. Both ‘‘ and ‘‘ characters should be escaped
  2. The xml content should be kept as a single line

Json import data can be loaded into Solr by the curl command,

curl 'http://localhost:8983/solr/update/json?commit=true' --data-binary @books.json -H 'Content-type:application/json'

Or, by using solrj:

CommonsHttpSolrServer server = new CommonsHttpSolrServer(serverpath);
ContentStreamUpdateRequest csureq = new ContentStreamUpdateRequest("/update/json");
NamedList<Object> result = server.request(csureq);
NamedList<Object> responseHeader = (NamedList<Object>) result.get("responseHeader");

Integer status = (Integer) responseHeader.get("status");

Stripping out xml tags in Schema definition

When querying xml content, we most likely will not be interested in xml tags. So we need to strip out xml tags before indexing the xml text. We can do that by applying HTMLStripCharFilter to the xml content.
            <analyzer type="index">
            <analyzer type="query">

Search XML Content

Xml content search does not differ much from text content search. However, if people want to search for xml attributes, there requires some special tweak.

HTMLStripCharFilter we mentioned earlier will filter out all xml tags including attributes, in order to index attributes, we need to find a way to make HTMLStripCharFilter keep the attribute text.

For example if we have original xml content as following,

<sample attr=”key_o2_4”>find it </sample>
After applying HTMLStripCharFilter, we want to have,

key_o2_4    find it
One way we can do is to add assistance xml instruction tags in original xml content such as,

<sample attr=”key_o2_4”><?solr key_o2_4?>find it</sample>

And apply Solr.PatternReplaceCharFilterFactory to it as shown in following schema fieldtype definition.

<analyzer type="index">
<charFilter pattern="&lt;?solr ([A-Z0-9_-]*)?&gt; " replacement="       $1  " maxBlockChars="10000000"/>

Which will make replace <?solr key_o2_4?> with 7 leading empty spaces + key_o2_4 + 2 ending empty spaces in order to keep the original offset,

With this technique, we can do a search on attr attribute and get a hit.

Do you have questions? Visit our website or contact us for more information.

ExternalFileField in Solr

Sometimes we want to update document values in an indexed field more often than other fields. A good solution to this is to use the field type ExternFileField. The ExternalFileField gets values from an external file instead of the index. Such file can easily be changed and update the field after a commit. Hence no documents need to be re-indexed. A field that has ExternalFileField as type is not searchable. The field may currently only be used as a ValueSource in a FunctionQuery.

The external file contains keys and values:


The keys don’t need to be unique.

The name of the external file must be external_<fieldname> or external_<fieldname>.* and must be placed in the index directory.

A new file type of the type ExternalFileField and field must be added to schema.xml.

<fieldType name="file"

           keyField="keyField" defVal="1" indexed="false"

           stored="false" valType="float" />

<field name="<fieldname>" type="file" />

keyField is the field that contains the keys and <fieldname> contains the values from the external file.

valType defines the value type of the field.

At Findwise we have used this method for a customer where we wanted to show the most visited pages higher up in the search result. These statistics are changing daily for a lot of pages and we don’t want to re-index all these pages every day.

SPC09 Day 2 – FAST Search for SharePoint Made “SharePoint Easy”

After a great evening with Microsoft Sweden touring around Las Vegas, having dinner at the Stratosphere and a good night sleep today’s session started of. Today’s focus has been deep dives in to the different areas. For me it has been deep dives in Sharepoint Search and FAST Search for Sharepoint.

First of was sessions about Sharepoint Search functions and depolyment. This was more or less going through the different functionality that I wrote about yesterday. A thew new things did thou come up, things like crawler policy’s, avoiding that your index is empties just because the web site that you crawl is on service during crawl time, connector framework that now supports developing connectors in .NET and configuration of the whole search service through PowerShell.

But now to the more exiting thing, FAST Search for SharePoint 2010. This something that it has been really quite about. It has gone 18 months since the acquisition of FAST and during that time not much information about the upcoming version has leaked out. But from yesterday everything is made public. There is even gona come a public beta of FAST Search for SharePoint in November for everyone to test it out.

The most exiting thing about this new version of FAST is that it’s almost completely integrated within SharePoint. With almost is that the installation of FAST is still done on separated servers and has it’s own installation program, though simplified. But after completion of installation and node setup (done in a deployment.xml config file) everything is done in the SharePoint central administration interface or through PowerShell. There is not even the possibility any longer to make configurations through config files in the installation of FAST. Some more advanced configurations and extensions can be made through .NET libraries and PowerShell, for example document processing steps. I will know more about this after tomorrows sessions.

Connectors in new FAST are no longer used as before. They are integrated into SharePoint instead. It’s even the same connector for SharePoint search and FAST Search for SharePoint. Setup is done in the same way to ease the transition from SharePoint Search to FAST.

People search in SharePoint 2010 will, even though you use FAST Search For SharePoint, be handled by SharePoint search. And as Jeff Fried sad “why try to set this up in FAST Search for SharePoint when the people search in SharePoint already is amazing”.

Now it’s time for one of the biggest beach parties that Las Vegas ever has hosted here at Mandal Bay Hotel. Over 7000 crazy SharePoint geeks are going to rock there pants of to the sound of the 80’s.