Relevancy is the measure of how well a set of documents (results) answers or addresses the intent of a given query.
When there are many query matches, the search engines must rank the results by relevance score, sorting the results listing so that the pages most likely to be useful will appear first. Varying algorithms are used to define relevancy. Relevancy definition and tuning is one of core differentiators of FAST ESP platform. This blog post is about the relevance framework and related concepts and features in FAST ESP.
FAST ESP Search Relevance Framework
FAST ESP applies search relevancy through the following key steps:
The relevancy of a document with respect to a query is represented by a ranking value. Following section lists the different elements used to calculate the rank value.
Elements of Rank Value
Age of a document compared to the time when the query is issued
Importance of a document determined by the links to it from other documents
Assigned importance of a document, independent of the query
Importance of geographical distance between a document’s associated latitude/longitude and a target location specified in a query
Importance of matching a query in a given document field
For multi-term queries: the shorter the distance between query terms in a document, the higher the document’s rank value
The earlier a query term occurs in a field, the higher the document’s rank value
The more frequent a query term occurs in a document, the higher the document’s rank value
The greater the number of query terms present in the same field of a matching document, the higher the document’s rank value
For multi-term queries; the more query terms matched in a document, the higher the document’s rank value
Relevant Sorting of Query Results
FAST ESP provides three main methods for sorting the results of a query:
A Rank Profile concept enables full control of the relative weight of each rank component for a given query. For example, how important an article’s title is relative to the main text or how important is proximity versus freshness. This enables individual relevance tuning of different query applications using a FAST ESP installation.
In FAST ESP, the Rank Profile is a configuration element within the Index Profile and defines relative weight for the different components of the dynamic rank. Multiple Rank Profiles can be specified in the Index Profile.
Tuning the Ranking and Sorting of Query Results
The ranking and sorting of query results can be tuned in three main ways:
Relevance support in the Query Language
FAST ESP includes a highly expressive query language that also includes advanced proximity operators:
Dynamic Client Side Ranking
Dynamic client side ranking can be done by using the XRANK operator which is a part of the FAST Query Language (FQL). The boost value is specified with the parameter boost=n, where n is some signed integer value. Negative boost is supported, but if the result of boosting with a negative value is negative then the result will be set to 0.
Its a concept unique to FAST and I will cover it in detail in another post.
Rank Modification Tools
FAST ESP provides tools to modify rank for individual documents. These tools enable you to perform Absolute Query Boost, Relative Query Boost or Relative Document Boost for given documents in the FAST ESP index. An example could be a product database where it may be desired to boost products with highest profit margins, boost products related to campaigns, etc.
Two main tools exist for this purpose:
1) Search Business Center (SBC) - This is an optional, GUI based tool which enables query-oriented rank tuning. The SBC also includes a powerful query reporting module that may be used to assist in the rank tuning. Using the SBC you can change the ranking for each query using three different methods:
2) Rank Tuning Bulk Loader - This is a standard FAST ESP tool that enables you to perform the same rank tuning as the SBC, using an XML file as input. The XML file contains a specification of the rank modifications to be performedHow SharePoint does Relevancy?
Relevancy in SharePoint 2007
SharePoint 2007 also has Search Relevance architecture though the sophistication and flexibility is much less than FAST ESP. You can refer to SharePoint SDK documentation - Enterprise Search Relevance Architecture Overview for details on it. Also refer to Improving Relevance to learn some of the ways you can adjust the settings used in ranking calculation for Enterprise Search results, as well as other techniques you can try for improving relevance.
PingBack from http://iworker.cz/2009/05/03/fast-and-sharepoint-2007.html