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 |
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