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Dynamic rank (FAST Search Server 2010 for SharePoint)

FAST Search Server 2010
 

Applies to: FAST Search Server 2010

Topic Last Modified: 2011-03-28


Dynamic rank is calculated at search time. The dynamic rank score is calculated based on a combination of the input search words and the rank profile configuration. You can control the effect of the dynamic rank points by modifying the weight of different components in the rank profile.

You can modify the following components in the rank profile to effect dynamic rank points:

  • Freshness: Rank points given based on the age (last modified) of the item compared to the time of the search. The resolution used (second/minutes/hour/day/year) is important when calculating rank, because a lower resolution implies that smaller time differences will have a larger effect on ranking.

  • Context: Rank points given based on where in the search item the search words match. The different managed properties such as title and body are mapped to different importance levels. This makes it possible to give more rank points for a search word match in a title than in the body text of the search item. Context boost is assigned as an overall weight and as a weight for a specific managed property.

  • Proximity: Rank points given depending on the distance between the search words and where these words are located in the search item. For example, if two search words appear in the same managed property within the full-text index, they will get more rank points.

  • Managed Property Field Boost: Rank points given based on a specific item type of a managed property. For example, if you want to give additional rank points to indexed items of a specific type such as Word documents, you can give search items with the file extension .docx additional rank points.

  • Authority (anchor text): Rank points given based on when a search word occurs in the link text (anchor text) of a link pointing to the search item. This rank boost has two components:
    Partial match - the link text is Microsoft Word, and the search word is Microsoft.
    Complete match - additional score if there is a match between the search word and link text.

  • Query authority (click-through): Rank points given based on when a search word matches search items associated with previously performed searches (click-through). In the search front-end, all of a user’s searches and the search items that the user clicks on that are associated with those searches, are stored and processed. For example, if a user searched for vacation and clicked on the vacation request template in the search result (for example http://myserver/template/vacation.aspx), this URL is associated with the search word and obtains additional rank points when any new search with the same search word is performed. Processing occurs one time per day. The last 30 days of clicks are kept for processing. This rank boost has two components:
    Partial match - the initial search words that resulted in a click to this item was Microsoft Word, and the search word now is Microsoft.
    Complete match - an additional score if there is a match between the search word and link text.

For search performance reasons, the calculated dynamic rank score is based on different importance levels in the full-text index. Drilling, or going to the next level, occurs when the number of matching search items for a search word is larger than the StopWordThreshold for the rank profile that is being used. Drilling works with the StopWordThreshold to ensure that the most relevant items are returned first when the stop word threshold is reached.

For information about how to tune dynamic rank, see Tune dynamic rank (FAST Search Server 2010 for SharePoint)

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