We present a probabilistic relational algebra (PRA) which is a generalization of standard relational algebra. Here tuples are assigned probabilistic weights giving the probability that a tuple belongs to a relation. Based on intensional semantics, the tuple weights of the result of a PRA expression always confirm to the underlying probabilistic model. We also show for which expressions extensional semantics yields the same results. Furthermore, we discuss complexity issues and indicate possibilities for optimization. With regard to databases, the approach allows for representing imprecise attribute values, whereas for information retrieval, probabilistic document indexing and probabilistic search term weighting can be modelled. As an important extension, we introduce the concept of vague predicates which yields a probabilistic weight instead of a Boolean value, thus allowing for queries with vague selection conditions. So PRA implements uncertainty and vagueness in combination with the...

In this paper, an introduction and survey over probabilistic information retrieval (IR) is given. First, the basic concepts of this approach are described: the probability ranking principle shows that optimum retrieval quality can be achieved under certain assumptions; a conceptual model for IR along with the corresponding event space clarify the interpretation of the probabilistic parameters involved. For the estimation of these parameters, three different learning strategies are distinguished, namely query-related, document-related and description-related learning. As a representative for each of these strategies, a specific model is described. A new approach regards IR as uncertain inference; here, imaging is used as a new technique for estimating the probabilistic parameters, and probabilistic inference networks support more complex forms of inference. Finally, the more general problems of parameter estimation, query expansion and the development of models for advanced document representations are discussed.

Multimedia repositories and applications that retrieve multimedia information are becoming increasingly popular. In this paper, we study the problem of selecting objects from multimedia repositories, and show how this problem relates to the processing and optimization of selection queries in other contexts, e.g., when some of the selection conditions are expensive user-defined predicates. We find that the problem has unique characteristics that lead to interesting new research questions and results. This article presents an overview of the results in [1]. An expanded version of that paper is in preparation [2]. 1 Query Model In this section we first describe the model that we use for querying multimedia repositories. Then, we briefly review related models for querying text and image repositories. 1.1 Our Query Model In our model, a multimedia repository consists of a set of multimedia objects, each with a distinct object identity. Each multimedia object has a set of attributes, like...

Repositories of multimedia objects having multiple types of attributes (e.g., image, text) are becoming increasingly common. A query on these attributes will typically request not just a set of objects, as in the traditional relational query model (filtering), but also a grade of match associated with each object, which indicates how well the object matches the selection condition (ranking). Further- more, unlike in the relational model, users may just want the k top-ranked objects for their selection queries, for a relatively small k. In addition to the differences in the query model, another peculiarity of multimedia repositories is that they may allow access to the attributes of each object only through indexes. In this paper, we investigate how to optimize the processing of top-k selection queries over multimedia repositories. The access characteristics of the repositories and the above query model lead to novel issues in query optimization. In particular, the choice of the indexes used to search the repos- itory strongly influences the cost of processing the filtering condition. We define an execution space that is search-minimal, i.e., the set of indexes searched is minimal. Although the general problem of picking an optimal plan in the search-minimal execution space is NP-hard, we present an efficient algorithm that solves the problem optimally with respect to our cost model and execution space when the predicates in the query are independent. We also show that the problem of optimizing top-k selection queries can be viewed, in many cases, as that of evaluating more traditional selection conditions. Thus,

In this paper, it is shown that fuzzy sets and possibility theory provide an homogeneous framework for the representation of both imprecise/uncertain information and soft queries with a flexible interpretation. Incompletely known information as well as flexible query handling capabilities are expected to extend the range of applications for future database management systems. The term fuzzy databases which is extensively used in the specialized literature covers several different meanings which are reviewed. A special emphasis is put on flexible queries addressed to regular databases. Such queries enables the user to easily express preferences among more or less admissible attribute values. Several approaches for introducing flexibility, including fuzzy sets, are compared. A query language based on SQL is outlined and some issues related to query processing are discussed. In addition, possibility theory proves to be useful for representing imperfectly known data and soft constraints. P...

: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : xii 1. INTRODUCTION : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1 1.1 Digital Libraries : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1 1.2 Visual Information Systems : : : : : : : : : : : : : : : : : : : : : : : 1 1.3 Image Databases : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2 1.3.1 Characteristics of Image Data : : : : : : : : : : : : : : : : : : 5 1.3.2 Similarity Matches : : : : : : : : : : : : : : : : : : : : : : : : 5 1.3.3 Query Types : : : : : : : : : : : : : : : : : : : : : : : : : : : 5 1.3.4 Multiple Interpretations of an Image : : : : : : : : : : : : : : 7 1.3.5 Image Databases in a Distributed Environment : : : : : : : : 7 1.4 Motivation : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 8 1.4.1 Thesis Statement : : : : : : : : : : : : : : : : : : : : : : : : : 9 1.5 Thesis Overview : : : : : : : : : : : : : : : : : : : : : : : : : : : : : ...

We describe a prototype for an information system that integrates text and fact retrieval. A query is a set of conditions which relate either to the text or the attribute values of a database object. Conditions may be assigned weights w.r.t. the query as well as to an object. These weights form the basis for a ranking of the database objects w.r.t. the query. As user interface, the system provides a menu-oriented browser.

this paper, we present then the VISU model which is the result of our on going research in this domain. This model capitalizes amount of work made in the field of information retrieval, notably the use of Conceptual Graphs [4]. We show how the VISU model adapts and extends these results in order to satisfy the constraints inherent to the video medium. Our objective is to annotate videos using Conceptual Graphs in order to represent complex descriptions associated with frames or segments of frames of the video. Then, we take advantage of the material implication of Conceptual Graphs on which is based an efficient graph matching algorithm [5] which allows to formulate queries. We propose a query formalism that provides a way to specify retrieval criteria. These criteria are useful to users for adapting the summary to their specific requirements. The principles of the query processing are also presented. Finally, we discuss about time constraints that must be solved to create a summary with a given duration

Document Bases are large repositories of unstructured data in form of individual documents. Along current Document Bases proposals a general purpose system can not be found. These systems have been built for specific applications and, therefore their architecture is not flexible to be used for alternative applications. In the state of art for Document Bases, it has become of prime importance the development of a model able to include all the features desirable to represent any kind of application requiring storage of documents.