Google Search Appliance Creating the Search Experience - Manual (Page 70)

Google Search Appliance: Creating the Search Experience Best Practices 70
Using Source Biasing
Using source biasing, you can boost or weaken the relevancy score of a document that belongs to a
specified collection, matches certain URL patterns, or is fed from a data source. Boosting a score usually
moves a result up in the rankings. Weakening a score usually moves it down. The search appliance
offers two controls over source biasing, as described in the following table.
For example, suppose most official content in your organization is drafted in Microsoft Word (.doc), but
published in Portable Document Format (pdf). In some instances, both the .doc and .pdf versions of
documents have the same content. However, each type of document is stored in a different location.
• Microsoft Word documents are stored on www.mediacompany.com/drafts
• PDF documents are stored on www.mediacompany.com/publications
Both types of documents are crawled and appear in the search index. However, you want .pdf versions
to be higher in the search results than .doc versions. You create a result biasing policy where you can
influence the score of .pdf documents. For this result biasing policy, you can use source biasing to:
• Boost www.mediacompany.com/publications by setting a strong increase
• Weaken www.mediacompany.com/drafts by setting a weak decrease
By adjusting the strength of individual URLs you influence the score that reflects the relevance of
documents that match the URL patterns. After you select the result biasing policy for use with a front
end, .pdf documents are more likely to appear closer to the top of results listings.
The effect of changing a document's score is not always predictable. The order of a search result among
the other results is determined by many factors, including the scores of the other documents with
which it is returned.
Using Date Biasing
Using date biasing, you can specify the influence date biasing has in increasing the scores of more
recent documents relative to older documents. The default influence is No influence. You can change
this to one of ten settings in a range of More influence for a search appliance.
For example, suppose the mediacompany.com search index contains all DVD reviews written during the
past ten years. Typically, end users are interested in only searching the most recent reviews. However,
staff is interested in searching for all reviews.
You have created a front end for end users and another front end for staff. In the front end for end
users, you create a result biasing policy where you can configure date biasing to increase the rankings of
new documents and lower the rankings of legacy documents. After you select the result biasing policy
for use with the front end, documents with a more recent date are more likely to appear closer to the
top of results listings.
Control Description
Influence Specifies how much influence source biasing has in calculating scores for results
rankings overall. The default influence is No influence. You can change this to one
of ten settings in a range of More influence for a search appliance.
Strength Specifies how much influence source biasing has in calculating scores for
documents that match specific URL patterns. The default strength is Leave
unchanged. You can change this to Strong, Medium, or Weak increase or Strong,
Medium, or Weak decrease for each collection or specified URL pattern.