An information retrieval approach for approximate queries

With the growing availability of online information systems, a need for user interfaces that are flexible and easy to use has arisen. For such type of systems, an interface that allows the formulation of approximate queries can be of great utility since these allow the user to quickly explore the database contents even when he is unaware of the exact values of the database instances. Our work focuses on this problem, presenting a new model for ranking approximate answers and a new algorithm to compute the semantic similarity between attribute values, based on information retrieval techniques. To demonstrate the utility and usefulness of the approach, we perform a series of usability tests. The results suggest that our approach allows the retrieval of more relevant answers with less effort by the user.     

Exploiting syntactic analysis of queries for information retrieval

Up to now, the results of applying sophisticated NL techniques to information retrieval (IR) have been mostly disappointing. Our research aims at investigating in detail the role of syntactic analysis in IR and at finding answers to the question why it works better for some queries and worse for others. The final goal is a hybrid algorithm that selectively applies syntactic analysis to certain classes of queries while relying on standard statistical techniques otherwise.     

Optimal configurations for peer-to-peer user-private information retrieval

User-private information retrieval systems should protect the user’s anonymity when performing queries against a database, or they should limit the servers capacity of profiling users. Peer-to-peer user-private information retrieval (P2P UPIR) supplies a practical solution: the users in a group help each other in doing their queries, thereby preserving their privacy without any need of the database to cooperate. One way to implement the P2P UPIR uses combinatoric configurations to administrate the keys needed for the private communication between the peers.This article is devoted to the choice of the configuration in this system. First of all we characterize the optimal configurations for the P2P UPIR and see the relationship with the projective planes as described in finite geometry. Then we give a very efficient construction of such optimal configurations, i.e. finite projective planes. We finally check that the involved graphs are Ramanujan graphs, giving an additional justification of the optimality of the constructed configurations.     

Pictorial information retrieval using the random neural network

A technique is developed based on the use of a neural network model for performing information retrieval in a pictorial information system. The neural network provides autoassociative memory operation and allows the retrieval of stored symbolic images using erroneous or incomplete information as input. The network used is based on an adaptation of the random neural network model featuring positive and negative nodes and symmetrical behavior of positive and negative signals. The network architecture considered has hierarchical structure and allows two-level operation during learning and recall. An experimental software prototype, including an efficient graphical interface, has been implemented and tested. The performance of the system has been investigated through experiments under several schemes concerning storage and reconstruction of patterns. These schemes are either based on properties of the random network or constitute adaptations of known neural network techniques     

Optimal tree lists for information storage and retrieval

Combining the concepts of doubly-chained tree and list one may produce files with expected search time smaller than that of the pure tree. A best such structure is found to lie within a very large set of candidates, but a sort of convexity property is found to prevail and it is possible to devise extremely efficient solution procedures for even quite large problems of this variety.     

Film clips retrieval using image queries

The emergence of entertainment industry motivates the explosive growth of automatically film trailer. Manually finding desired clips from these large amounts of films is time-consuming and tedious, which makes finding the moments of user major or special preference becomes an urgent problem. Moreover, the user subjectivity over a film makes no fixed trailer caters to all tastes. This paper addresses these problems by posing a query-related film clip extraction framework which optimizes selected frames not only meet the semantic meaning of the queries but also have visual similarity on appearance between the query and selected clips. The experimental results show that our query-related film clip retrieval method is particularly useful for film editing, e.g. automatically finding movie clips to arouse audiences’ interests on the film.

     

Logical errors in database SQL retrieval queries

SQL is often used to express questions imposed by users. It is well known that this process is not error-free in that it may result in syntactically or semantically incorrect SQL queries. This article is meant to probe deeper into SQL queries that are incorrect, due to delusion errors. A classification of natural language questions will be introduced. The purpose of this classification is two-fold. Firstly, it gives insight into possible errors and enables us to distinguish between types of errors. Secondly, it is a means of determining the influence of measures (for instance, SQL training) that can be taken to reduce the number of aforementioned errors. For discussion, several of these measures will be presented and related to the classification.Abbreviations RA Relational algebra - SQL structured query language     

Synthesizing queries for handwritten word image retrieval

We propose a method to perform text searches on handwritten word image databases when no ground-truth data is available to learn models or select example queries. The approach proceeds by synthesizing multiple images of the query string using different computer fonts. While this idea has been successfully applied to printed documents in the past, its application to the handwritten domain is not straightforward. Indeed, the domain mismatch between queries (synthetic) and database images (handwritten) leads to poor accuracy.Our solution is to represent the queries with robust features and use a model that explicitly accounts for the domain mismatch. While the model is trained using synthetic images, its generative process produces samples according to the distribution of handwritten features. Furthermore, we propose an unsupervised method to perform font selection which has a significant impact on accuracy. Font selection is formulated as finding an optimal weighted mixture of fonts that best approximates the distribution of handwritten low-level features. Experiments demonstrate that the proposed method is an effective way to perform queries without using any human annotated example in any part of the process.     

Evaluating refined queries in top-k retrieval systems

In many applications, users specify target values for certain attributes/features without requiring exact matches to these values in return. Instead, the result is typically a ranked list of "top k" objects that best match the specified feature values. User subjectivity is an important aspect of such queries, i.e., which objects are relevant to the user and which are not depends on the perception of the user. Due to the subjective nature of top-k queries, the answers returned by the system to an user query often do not satisfy the users need right away, either because the weights and the distance functions associated with the features do not accurately capture the users perception or because the specified target values do not fully capture her information need or both. In such cases, the user would like to refine the query and resubmit it in order to get back a better set of answers. While there has been a lot of research on query refinement models, there is no work that we are aware of on supporting refinement of top-k queries efficiently in a database system. Done naively, each "refined" query can be treated as a "starting" query and evaluated from scratch. We explore alternative approaches that significantly improve the cost of evaluating refined queries by exploiting the observation that the refined queries are not modified drastically from one iteration to another. Our experiments over a real-life multimedia data set show that the proposed techniques save more than 80 percent of the execution cost of refined queries over the naive approach and is more than an order of magnitude faster than a simple sequential scan.     

Optimal short-term population coding: when Fisher information fails

Efficient coding has been proposed as a first principle explaining neuronal response properties in the central nervous system. The shape of optimal codes, however, strongly depends on the natural limitations of the particular physical system. Here we investigate how optimal neuronal encoding strategies are influenced by the finite number of neurons N (place constraint), the limited decoding time window length T (time constraint), the maximum neuronal firing rate f(max) (power constraint), and the maximal average rate (f)(max) (energy constraint). While Fisher information provides a general lower bound for the mean squared error of unbiased signal reconstruction, its use to characterize the coding precision is limited. Analyzing simple examples, we illustrate some typical pitfalls and thereby show that Fisher information provides a valid measure for the precision of a code only if the dynamic range (f(min)T, f(max)T) is sufficiently large. In particular, we demonstrate that the optimal width of gaussian tuning curves depends on the available decoding time T. Within the broader class of unimodal tuning functions, it turns out that the shape of a Fisher-optimal coding scheme is not unique. We solve this ambiguity by taking the minimum mean square error into account, which leads to flat tuning curves. The tuning width, however, remains to be determined by energy constraints rather than by the principle of efficient coding.     

Context-sensitive queries for image retrieval in digital libraries

In this paper we show how to achieve a more effective Query By Example processing, by using active mechanisms of biological vision, such as saccadic eye movements and fixations. In particular, we discuss the way to generate two fixation sequences from a query image I _q and a test image I _t of the data set, respectively, and how to compare the two sequences in order to compute a similarity measure between the two images. Meanwhile, we show how the approach can be used to discover and represent the hidden semantic associations among images, in terms of categories, which in turn drive the query process.     

Optimal clip ordering for multi-clip queries

A multi-clip query requests multiple video clips be returned as the answer of the query. In many applications and situations, the order in which these clips are to be delivered does not matter that much to the user. This allows the system ample opportunities to optimize system throughput by using schedules that maximize the effect of piggybacking. In this paper, we study how to find such optimal schedules. In particular, we consider two optimization criteria: (i) one based on maximizing the number of piggybacked clips, and (ii) the other based on maximizing the impact on buffer space. We show that the optimal schedule under the first criterion is equivalent to a maximum matching in a suitably defined bipartite graph, and that under the second criterion, the optimal schedule is equivalent to a maximum matching in a suitably defined weighted bipartite graph. Our experimental results, which are based on realistic distributions, indicate that both kinds of optimal schedules can lead to a gain in throughput of over 300%. And yet the time taken to compute such an optimal schedule is negligible. Finally, we show how to deal with clips that are variable in length. Received: June 9, 1998 / Accepted October 13, 1998     

Dynamic queries for visual information seeking

Considers how dynamic queries allow users to “fly through” databases by adjusting widgets and viewing the animated results. In studies, users reacted to this approach with an enthusiasm more commonly associated with video games. Adoption requires research into retrieval and display algorithms and user-interface design. The author discusses how experts may benefit from visual interfaces because they will be able to formulate more complex queries and interpret intricate results     

Optimal prefix and suffix queries on texts

In this paper, we study a restricted version of the position restricted pattern matching problem introduced and studied by Mäkinen and Navarro [V. Mäkinen, G. Navarro, Position-restricted substring searching, in: J.R. Correa, A. Hevia, M.A. Kiwi (Eds.), LATIN, in: Lecture Notes in Computer Science, vol. 3887, Springer, 2006, pp. 703-714]. In the problem handled in this paper, we are interested in those occurrences of the pattern that lies in a suffix or in a prefix of the given text. We achieve optimal query time for our problem against a data structure which is an extension of the classic suffix tree data structure. The time and space complexity of the data structure is dominated by that of the suffix tree. Notably, the (best) algorithm by Mäkinen and Navarro, if applied to our problem, gives sub-optimal query time and the corresponding data structure also requires more time and space.     

Optimal parallel scheduling of M-way join queries

The problem of computing multirelation (M-way) join queries on uniprocessor architectures has been considered by many researchers in the past. This paper lays the necessary foundation for work involving optimization of M-way joins in parallel architectures. We explain the inadequacies of previous uniprocessor strategies and describe a more suitable formulation based on the concept of matching in graph theory to approach the problem in a parallel environment. It has been shown that the problem of optimizing M-way joins is an NP-hard problem and hence we would expect that in a parallel processing environment the search space of possible solutions (join schedules) would be enormous, especially when a variable number of processors are considered. Our strategy seeks to reduce the region to search by partitioning the search space according to the number of available processors. Based on this a significant portion of the search space, which will produce non-optimal join schedules, may be ignored.     

Language-oriented information retrieval

There is no task that computers regularly perform that is more affected by the nature of human language than the retrieval of texts in response to a human need. Despite this, the techniques actually in use for this task, as well as most of the techniques proposed by information retrieval (IR) researchers, make little use of knowledge about language. In this article we take the view that IR is an inference task, and that natural language processing (NLP) techniques can produce text representations that enable more accurate inferences about document content. By considering previous work on language-based and knowledge-based techniques from this perspective, some clear lessons are apparent, and we are applying these lessons in the ADRENAL (Augmented Document REtrieval using NAtural Language processing) project. Our initial experiments with hand-coded representations suggest that using NLP-produced representations can result in significant performance increases in IR systems, and also demonstrate the attention that must be given to representational issues in language-oriented IR.