Tech Tip: Flexible Query Expansion Policies

Posted by Nitin Mangtani, Product Manager, Enterprise Search

The Google Search Appliance can automatically expand a search-users query by adding synonyms and words with the same stem. For example if a user enters car then search appliance will automatically search for car or cars. Administrators also have ability to custom upload their synonyms file or blacklist certain terms. So if you have a product which was originally called "product abc" and is now called "product xyz" you can create a synonyms file with these terms, as a result any searches for keyword "product abc" will automatically return relevant documents that contain the terms "product abc" or "product xyz". The end-result of query expansion is that search users find richer set of relevant results without having to re-query with different combination of terms.

You can log-in to the administrative console of Google Search Appliance and enable the Query Expansion feature. We provide you with 4 flexible options and these are:
None - This is by default and it disables the query expansion feature completely.
Standard: Enables query expansion, using Google's built-in synonyms.
Local: Enables query expansion, using only the synonyms that you upload to the appliance.
Full: Enables query expansion, using both Google's built-in synonyms and the files that you upload to the appliance.

Here is the example of the custom synonyms file uploaded to search appliance.
#Synonyms file created Oct 2006
#Author: nitinm
product abc = product xyz
FED = federal electronics division
{phone, cell, mobile, telephone}

There are two formats we support for the synonyms file
Format 1: term1 operator term2
In this format:
• term1 consists of one word or multiple words that are separated by single spaces.
• term2 consists of one word or multiple words that are separated by single spaces.
• operator is one of the following:
= Specifies that the words are equivalent. The appliance expands a search query for term1 or term2 by adding the other term.
> Causes the appliance to add term2 when a search query contains term1.

Entry format 2: {term, term, ...}
In this format:
• Each term in the list will be used to expand queries for each other term.
• The use of brackets {} was introduced with the current release

And finally you can create the blacklists file to mark certain words that should not be expanded. The blacklists file is applicable to both Google built-in synonyms and your custom synonyms file.

As you could see from the examples, we provide you a flexible way to create the synonyms file and also let you choose the policies that are applicable to your environment. The Google built-in synonyms file is also very rich and should be enabled. We recommend using the Full option to enable both Google built-in synonym file and your custom synonym file. So besides uploading / enabling new query expansion files, don't forget to enable it in your front end via the admin console.

We look forward to seeing happier search users.