2,262 research outputs found
Counterfactual Estimation and Optimization of Click Metrics for Search Engines
Optimizing an interactive system against a predefined online metric is
particularly challenging, when the metric is computed from user feedback such
as clicks and payments. The key challenge is the counterfactual nature: in the
case of Web search, any change to a component of the search engine may result
in a different search result page for the same query, but we normally cannot
infer reliably from search log how users would react to the new result page.
Consequently, it appears impossible to accurately estimate online metrics that
depend on user feedback, unless the new engine is run to serve users and
compared with a baseline in an A/B test. This approach, while valid and
successful, is unfortunately expensive and time-consuming. In this paper, we
propose to address this problem using causal inference techniques, under the
contextual-bandit framework. This approach effectively allows one to run
(potentially infinitely) many A/B tests offline from search log, making it
possible to estimate and optimize online metrics quickly and inexpensively.
Focusing on an important component in a commercial search engine, we show how
these ideas can be instantiated and applied, and obtain very promising results
that suggest the wide applicability of these techniques
News Session-Based Recommendations using Deep Neural Networks
News recommender systems are aimed to personalize users experiences and help
them to discover relevant articles from a large and dynamic search space.
Therefore, news domain is a challenging scenario for recommendations, due to
its sparse user profiling, fast growing number of items, accelerated item's
value decay, and users preferences dynamic shift. Some promising results have
been recently achieved by the usage of Deep Learning techniques on Recommender
Systems, specially for item's feature extraction and for session-based
recommendations with Recurrent Neural Networks. In this paper, it is proposed
an instantiation of the CHAMELEON -- a Deep Learning Meta-Architecture for News
Recommender Systems. This architecture is composed of two modules, the first
responsible to learn news articles representations, based on their text and
metadata, and the second module aimed to provide session-based recommendations
using Recurrent Neural Networks. The recommendation task addressed in this work
is next-item prediction for users sessions: "what is the next most likely
article a user might read in a session?" Users sessions context is leveraged by
the architecture to provide additional information in such extreme cold-start
scenario of news recommendation. Users' behavior and item features are both
merged in an hybrid recommendation approach. A temporal offline evaluation
method is also proposed as a complementary contribution, for a more realistic
evaluation of such task, considering dynamic factors that affect global
readership interests like popularity, recency, and seasonality. Experiments
with an extensive number of session-based recommendation methods were performed
and the proposed instantiation of CHAMELEON meta-architecture obtained a
significant relative improvement in top-n accuracy and ranking metrics (10% on
Hit Rate and 13% on MRR) over the best benchmark methods.Comment: Accepted for the Third Workshop on Deep Learning for Recommender
Systems - DLRS 2018, October 02-07, 2018, Vancouver, Canada.
https://recsys.acm.org/recsys18/dlrs
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Local search: A guide for the information retrieval practitioner
There are a number of combinatorial optimisation problems in information retrieval in which the use of local search methods are worthwhile. The purpose of this paper is to show how local search can be used to solve some well known tasks in information retrieval (IR), how previous research in the field is piecemeal, bereft of a structure and methodologically flawed, and to suggest more rigorous ways of applying local search methods to solve IR problems. We provide a query based taxonomy for analysing the use of local search in IR tasks and an overview of issues such as fitness functions, statistical significance and test collections when conducting experiments on combinatorial optimisation problems. The paper gives a guide on the pitfalls and problems for IR practitioners who wish to use local search to solve their research issues, and gives practical advice on the use of such methods. The query based taxonomy is a novel structure which can be used by the IR practitioner in order to examine the use of local search in IR
Modeling Temporal Evidence from External Collections
Newsworthy events are broadcast through multiple mediums and prompt the
crowds to produce comments on social media. In this paper, we propose to
leverage on this behavioral dynamics to estimate the most relevant time periods
for an event (i.e., query). Recent advances have shown how to improve the
estimation of the temporal relevance of such topics. In this approach, we build
on two major novelties. First, we mine temporal evidences from hundreds of
external sources into topic-based external collections to improve the
robustness of the detection of relevant time periods. Second, we propose a
formal retrieval model that generalizes the use of the temporal dimension
across different aspects of the retrieval process. In particular, we show that
temporal evidence of external collections can be used to (i) infer a topic's
temporal relevance, (ii) select the query expansion terms, and (iii) re-rank
the final results for improved precision. Experiments with TREC Microblog
collections show that the proposed time-aware retrieval model makes an
effective and extensive use of the temporal dimension to improve search results
over the most recent temporal models. Interestingly, we observe a strong
correlation between precision and the temporal distribution of retrieved and
relevant documents.Comment: To appear in WSDM 201
How users assess web pages for information-seeking
In this paper, we investigate the criteria used by online searchers when assessing the relevance of web pages for information-seeking tasks. Twenty four participants were given three tasks each, and indicated the features of web pages which they employed when deciding about the usefulness of the pages in relation to the tasks. These tasks were presented within the context of a simulated work-task situation. We investigated the relative utility of features identified by participants (web page content,structure and quality), and how the importance of these features is affected by the type of information-seeking task performed and the stage of the search. The results of this study provide a set of criteria used by searchers to decide about the utility of web pages for different types of tasks. Such criteria can have implications for the design of systems that use or recommend web pages
Temporal Information Models for Real-Time Microblog Search
Real-time search in Twitter and other social media services is often biased
towards the most recent results due to the “in the moment” nature of topic
trends and their ephemeral relevance to users and media in general. However,
“in the moment”, it is often difficult to look at all emerging topics and single-out
the important ones from the rest of the social media chatter. This thesis proposes
to leverage on external sources to estimate the duration and burstiness of live
Twitter topics. It extends preliminary research where itwas shown that temporal
re-ranking using external sources could indeed improve the accuracy of results.
To further explore this topic we pursued three significant novel approaches: (1)
multi-source information analysis that explores behavioral dynamics of users,
such as Wikipedia live edits and page view streams, to detect topic trends
and estimate the topic interest over time; (2) efficient methods for federated
query expansion towards the improvement of query meaning; and (3) exploiting
multiple sources towards the detection of temporal query intent. It differs from
past approaches in the sense that it will work over real-time queries, leveraging
on live user-generated content. This approach contrasts with previous methods
that require an offline preprocessing step
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