FAST Search for SharePoint 2010: Relevancy Tuning

Static rank points, also known as quality rank points, are added to search items before it is indexed. The number of points given is based on boost values that are stored in predefined static/quality rank components. You can decide which of these components to use at search time so that you only get the rank points from the components that you specify. You can control the effect of the static rank points by modifying the weight of the different components. Static rank points assigned to an indexed item are independent of the search words that are used, so static rank only indicates something about the general importance of an item. Adding static rank points is efficient from a search performance point of view because it does not add any complexity to the search evaluation.

Static rank points are derived from multiple managed properties. The following sets of managed properties are predefined for static ranking:

• Urldepthrank: Rank points given to boost shorter URLs.
• Docrank: Rank points given based on the number of and relative importance of links pointing to an item.
• Siterank: Rank points given based on the number of and relative importance of links pointing to the items on a site.
• Hwboost: FAST Search Server 2010 for SharePoint placeholder for generic usage of quality rank points.

In addition to these managed properties, you can add any custom integer managed property to the list of static/quality rank properties.

http://technet.microsoft.com/en-us/library/ff191247.aspx

Microsoft FAST Search Server 2010 offers a more powerful enterprise search for SharePoint 2010. Combining the power of FAST and simplicity of SharePoint, FAST Search Server 2010 offers an exceptional intranet and people search experience. It also serves as a platform for building search-driven applications.

The most powerful feature FAST offers for SharePoint is relevancy tuning. FAST Search Server 2010 comes with a predefined relevance out of the box and is tuned against a large set of various sample data. However, the data is not scoped for users, locations, organizations, keywords or content types. The search administrator has the option to create custom relevancy models tuned to differences in content sources, application needs and user contexts.

FAST Search assigns a relevancy score to each search index. Tuning relevancy manipulates the scoring system for the FAST Search system in the following ways.

• Static (quality) rank: Rank points added to a search item before it is indexed.
  The number of points given is based on boost values that are stored in four predefined static/quality rank components. In addition, any custom integer managed property can also be used to tune static rank. You can decide which of these components to use at search time so that you only get the rank points from the components that you specify. You can control the effect of the static rank points by modifying the weight of the different components. Static rank points assigned to an indexed item are independent of the search words used, so static rank only indicates something about the general importance of an item.
• Dynamic rank: Rank points added to search items at search time.
  The number of points given is based on a combination of the search words used and boost values that are stored in dynamic rank components. You can control the effect of the dynamic rank points by modifying the weight of the different components.
• Keyword rank: Rank points added to an item when a search word matches a specified keyword.
  Recall is improved by searching for the associated synonyms. Also, the search experience is improved by displaying additional relevant information with using Best Bets and Visual Best Bets. Also, incorporating document and site promotions to move relevant search results higher up in the search results list.
• Linguistic features: Like stemming, spell checking, stop words and tokenization effect both relevance and recall.
• Fast Query Language (FQL): A query language intended for creating queries programmatically.
  FQL can be used only for solutions developed for FAST Search Server 2010 for SharePoint.

The dynamic rank is more powerful than static rank because the ranking points are assigned at the search time based on search query. This makes it the most commonly used option for relevancy tuning. Dynamic rank option allows for boosting rank points in any of the following components of the indexed item.

• Freshness: Rank points are given based on age of item.
• Context: Rank points are given based on the search word hits in the item.
• Proximity: Rank points are given based on distance between the search words hit in the item.
• Managed Property Field Boost: Rank points are given based on value of managed property.
• Authority (anchor text): Rank points are given based on when a search word retrieves hits in the link text.
• Query Authority (click-through): Rank points are given based on when a search retrieves hits in items associated with previously clicked on search results.

As described herein, relevancy tuning allows an organization to implement a search solution that takes into account many variables that cause the most relevant results to rank highest in a search.

This tip contributed by Khanh Hoang, Abel Solutions’ Senior SharePoint Consultant.