- Học viên: Phạm Thị Thu Thủy CNTT SUMMARY Databases and information systems are often hard to use because they do not explicitly attempt to cooperatewith their users. - Responses to queries may not contain the information the user really wants. - A user may need more information or might even need different information than the query requests. - Since a query language is used as a handy tool to obtain information from a database, users want more user-friendly and fault-tolerant query interfaces. - When a query search condition does not match with the underlying database, users would rather receive approximate answers than null information by relaxing the condition. - Personalization systems exploit preferences for providing users with only relevant data from the huge volume of information that is currently available. - We consider preferences that dependent on context, such as the location of the user. - Often, the context of the query may be too specific to match any of the given preferences. - In this paper, we consider possible expansions of the query context produced by relaxing one or more of its context attributes Besides beginning and conclusion, the content of the essay include 3 chapters: Chapter 1: Overview of query relaxtion. - This chapter researches the concept of relaxation and the format of relaxation, it describes query relaxtion process which is based on conceptual hierarchies. - Chapter 2: Query relaxtion based on KAH and KAD Học viên: Phạm Thị Thu Thủy CNTT This chapter introduces the conceptual clustering framework on the basis of a knowledge abstraction hierarchy (KAH) that captures not only value abstraction information but also domain abstraction information from the underlying database. - Based on the KAH, a knowledge abstraction database is constructed on a relational data model, and various cooperative query-answering mechanisms are explored using the generalization and specialization processes in the KAH. - This chapter describes user model of cooperative query answering system. - Chapter 3: On Relaxing Contextual Preference Queries This chapter shows us how to modeling and storing Context-Aware Preferences. - Besides, this chapter also introduces how to relaxing contextual preference queries
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