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{{Short description|Subfield of machine learning}}
'''Preference learning''' is a subfield of [[machine learning]] that focuses on modeling and predicting preferences based on observed preference information.<ref>{{Cite Mehryar Afshin Ameet 2012}}</ref> Preference learning typically involves [[supervised learning]] using datasets of pairwise preference comparisons, rankings, or other preference information.
==Tasks==
The main task in preference learning concerns problems in "[[learning to rank]]". According to different types of preference information observed, the tasks are categorized as three main problems in the book ''Preference Learning'':<ref>{{Cite
===Label ranking===
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In label ranking, the model has an instance space <math>X=\{x_i\}\,\!</math> and a finite set of labels <math>Y=\{y_i|i=1,2,\cdots,k\}\,\!</math>. The preference information is given in the form <math>y_i \succ_{x} y_j\,\!</math> indicating instance <math>x\,\!</math> shows preference in <math>y_i\,\!</math> rather than <math>y_j\,\!</math>. A set of preference information is used as training data in the model. The task of this model is to find a preference ranking among the labels for any instance.
It was observed that some conventional [[Classification in machine learning|classification]] problems can be generalized in the framework of label ranking problem:<ref>{{Cite
===Instance ranking===
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If we can find a mapping from data to real numbers, ranking the data can be solved by ranking the real numbers. This mapping is called [[utility function]]. For label ranking the mapping is a function <math>f: X \times Y \rightarrow \mathbb{R}\,\!</math> such that <math>y_i \succ_x y_j \Rightarrow f(x,y_i) > f(x,y_j)\,\!</math>. For instance ranking and object ranking, the mapping is a function <math>f: X \rightarrow \mathbb{R}\,\!</math>.
Finding the utility function is a [[Regression analysis|regression]] learning problem{{citation needed|date=March 2025}} which is well developed in machine learning.
===Preference relations===
The binary representation of preference information is called preference relation. For each pair of alternatives (instances or labels), a binary predicate can be learned by conventional
Using preference relations to predict the ranking will not be so intuitive. Since observed preference
==Uses==
Preference learning can be used in ranking search results according to feedback of user preference. Given a query and a set of documents, a learning model is used to find the ranking of documents corresponding to the [[relevance (information retrieval)|relevance]] with this query. More discussions on research in this field can be found in [[Tie-Yan Liu]]'s survey paper.<ref>{{Cite
Another application of preference learning is [[recommender systems]].<ref>{{Citation
==References==
{{Reflist
[[Category:Information retrieval techniques]]
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