Relational keyword search (R-KwS) systems based on schema graphs take the keywords from the input query, find the tuples and tables where these keywords occur and look for ways to "connect" these keywords using information on referential integrity constraints, i.e., key/foreign key pairs. The result is a number of expressions, called Candidate Networks (CNs), which join relations where keywords occur in a meaningful way. These CNs are then evaluated, resulting in a number of join networks of tuples (JNTs) that are presented to the user as ranked answers to the query. As the number of CNs is potentially very high, handling them is very demanding, both in terms of time and resources, so that, for certain queries, current systems may take too long to produce answers, and for others they may even fail to return results (e.g., by exhausting memory). Moreover, the quality of the CN evaluation may be compromised when a large number of CNs is processed. Based on observations made by other researchers and in our own findings on representative workloads, we argue that, although the number of possible Candidate Networks can be very high, only very few of them produce answers relevant to the user and are indeed worth processing. Thus, R-KwS systems can greatly benefit from methods for accessing the relevance of Candidate Networks, so that only those deemed relevant might be evaluated. We propose in this paper an approach for ranking CNs, based on their probability of producing relevant answers to the user. This relevance is estimated based on the current state of the underlying database using a probabilistic Bayesian model we have developed. Experiments that we performed indicate that this model is able to assign the relevant CNs among the top-4 in the ranking produced.In these experiments we also observed that processing only a few relevant CNs has a considerable positive impact, not only on the performance of processing keyword queries, but also on the quality of the results obtained.978-1-4799-7964-6/15/$31.00

No abstract

No abstract

Identifying record replicas in Digital Libraries and other types of digital repositories is fundamental to improve the quality of their content and services as well as to yield eventual sharing efforts. Several deduplication strategies are available, but most of them rely on manually chosen settings to combine evidence used to identify records as being replicas. In this paper, we present the results of experiments we have carried out with a novel Machine Learning approach we have proposed for the deduplication problem. This approach, based on Genetic Programming (GP), is able to automatically generate similarity functions to identify record replicas in a given repository. The generated similarity functions properly combine and weight the best evidence available among the record fields in order to tell when two distinct records represent the same real-world entity. The results of the experiments show that our approach outperforms the baseline method by Fellegi and Sunter by more than 12% when identifying replicas in a data set containing researcher's personal data, and by more than 7%, in a data set with article citation data.

No abstract

No abstract

This article discusses a novel approach developed for static index pruning that takes into account the locality of occurrences of words in the text. We use this new approach to propose and experiment on simple and effective pruning methods that allow a fast construction of the pruned index. The methods proposed here are especially useful for pruning in environments where the document database changes continuously, such as large-scale web search engines. Extensive experiments are presented showing that the proposed methods can achieve high compression rates while maintaining the quality of results for the most common query types present in modern search engines, namely, conjunctive and phrase queries. In the experiments, our locality-based pruning approach allowed reducing search engine indices to 30% of their original size, with almost no reduction in precision at the top answers. Furthermore, we conclude that even an extremely simple localitybased pruning method can be competitive when compared to complex methods that do not rely on locality information.

In this paper, we propose a set of similarity metrics for manipulating collections of values occuring in XML documents. Following the data model presented in TAX algebra, we treat an XML element as a labeled ordered rooted tree. Consider that XML nodes can be either atomic, i.e, they may contain single values such as short character strings, date, etc, or complex, i.e., nested structures that contain other nodes, we propose two types of similarity metrics: MAVs, for atomic nodes and MCVs, for complex nodes. In the first case, we suggest the use of several application domain dependent metrics. In the second case, we define metrics for complex values that are structure dependent, and can be distinctly applied for tuples and collections of values. We also present experiments showing the effectiveness of our method.