Configuring Retrieval - Controls¶
Controls are methods for configuring retrieval. Controls are set using the setControl() method in SearchRequest, and accessible to retrieval code via the Request object. They are re-read for every query, therefore, they allow the configuration of the search engine to be adjusted on a per-query basis.
Manager¶
| Control Name | Default | Description |
|—————-|———-|————————————————————|
| start | 0 | Offset of first document to be retrieved, 0-based |
| end | unset | Offset of last document to be retrieved, 0-based |
| wmodel | DPH | Name of the weighting model to use during retrieval |
| terrierql | on | Asks the Manager to parse an end-user query |
| parseql | on | Asks the Manager to map a parsed end-user query into MatchOp format |
| parsecontrols| on | Asks the Manager to remove any controls from the user’s query |
| matchopql | off | Asks the Manager to parse a MatchOp formatted query. When used, terrierql, parseql should be set to off |
| applypipeline| on | Asks the Manager to apply the term pipeline to the query |
| localmatching| on | Controls if matching should be applied to the query |
| matching | org.terrier.matching.daat.Full | Name of the matching class to run |
| decorate | on | Controls if decoration should occur, i.e. decorating the ResultSet with metadata |
| qe | off | Controls if query expansion should be applied |
| filters | on | Controls if any post-filters should be applied for the query |
| site | off | Performs hostname suffix matching as a PostFilter, like on web search engines. Requires the ResultSet to be decorated with “url” metadata |
| labels | off | Adds the labels to documents in the ResultSet, using org.terrier.learning.LabelDecorator. Require the qrels file to have been set, using property learning.labels.file. |
Weighting Models¶
| Control Name | Default | Description |
|—————-|———-|——————————————————————————-|
| bm25.b | 0.75 | Length normalisation parameter of BM25 |
| dfr.c | 1 | Length normalisation parameter of DFR weighting models based on Norm2, e.g. PL2 |
Query Expansion¶
QueryExpansion occurs when the qe control is set to on. From the batchretrieve commandline, this can be achieved using -q or -c qe:on arguments.
| Control Name | Default | Description |
|————–|———-|———————————————————–|
| qemodel | Bo1 | Name of the query expansion model |
| qe_fb_terms| 10 (obtained from property) | Number of expansion terms to add |
| qe_fb_docs | 3 (obtained from property) | Number of pseudo-relevance feedback documents to analyse |
Webpage: http://terrier.orgContact: School of Computing ScienceCopyright (C) 2004-2020 University of Glasgow. All Rights Reserved.