This paper discusses modelling, design and imple mentation issues for a knowledge-based information retrieval system Both the domain knowledge representation and the inference mechanism are based upon a fuzzy set theoretical framework The system manages natural language queries and returns a ranked set of relevant documents, computing for each of them a degree of support depending on multiple sources of evidence. In the following, after a brief remark about the need for modelling the inherent imprecision associated with the retrieval process, a model based on fuzzy reasoning is proposed. Then the architecture is presented of FIRST, a prototype system which is intended as an experimental test-bed for the applica tion of intelligent techniques in order to improve the effective ness of information retrieval systems Finally, we discuss im plementation details with reference to the retrieval component and related strategies that have been developed to reduce the impact of using imprecise knowledge upon the computational efficiency of the system.

In this paper, a fuzzy Object‐Oriented Data model (FOOD) is defined based on the extension of a Graph‐based Object model (D. Lucarella and A. Zanzi “A graph‐oriented data model,” in Database and Expert Systems Applications, R. Wagner and H. Toma, Eds., Springer‐Verlag, Berlin, 1996, pp. 197–206), in order to manage both crisp and imperfect information. These capabilities are requisites of many current applications dealing with data of different nature and with complex interrelationships. The model is based on a visual paradigm which supports both the representation of the data semantics and the direct browsing of the information. In the extended model both the database scheme and instances are represented as directed labeled graphs in which the fuzzy and uncertain information has its own representation. ©1999 John Wiley & Sons, Inc.

Document filing and retrieval systems can be designed using advanced techniques resulting from recent research in information retneval. In this paper, a document retneval system is presented, based upon the vector processing model. The system employs an automatic indexing procedure with a weighting scheme to reflect term importance. Documents are stored using an in verted file organization. Natural language quenes are sup ported with a retrieval strategy based on best match techniques and relevance feedback. The emphasis is on nearest neighbour searching to locate documents closest to a given query. That means, after having defined a sirrularitv function, the identification of those docu ments in the collection which exhibit a higher degree of re semblance to the query. The problem is introduced with reference to a straightfor ward search procedure that returns the nearest neighbour set manipulating the inverted file entnes. Then. an improved al gorithm is presented which optimizes both the number of documents to be evaluated and the number of inverted lists to be inspected.

We present a graph-based object model that may be used as a uniform framework for direct manipulation of multimedia information. After an introduction motivating tbe need for abstraction and structuring mechanisms in hypermedia systems, we introduce the data model and the notion of perspective, a form of data abstraction that acts as a user interface to the system, providing control over the visibility of the objects and their properties. A perspective is defined to include an intension and an extension, The intension is defined in terms of a pattern, a subgraph of the schema graph, and the extension is the set of pattern-matching instances. Perspectives, as well as database schema and instances, are graph structures that can be manipulated in various ways. The resulting uniform approach is well suited to a visual interface. A visual interface for complex information systems provides high semantic power, thus exploiting the semantic expressibility of the underlying data model, while maintaining ease of interaction with the system. In this way, we reach the goal of decreasing cognitive load on the user, with the additional advantage of always maintaining the same interaction style, We present a visual retrieval environment that effectively combines filtering, browsing, and navigation to provide an integrated view of the retrieval problem. Design and implementation issues are outlined for MORE (.Multimedia Object Retrieval Environment), a prototype system relying on tbe proposed model, The focus is on the main user interface functionalities, and actual interaction sessions are presented including schema creation, information loading, and information retrieval.