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Research on the nature of knowledge-based systems for bibliographic information retrieval is summarized. Knowledge-based search tactics are then considered in terms of their role in the functioning of a semantically based search system for bibliographic information retrieval, EP-X. This system uses such tactics to actively assist users in defining or refining their topics of interest. It does so by applying these tactics to a knowledge base describing topics in a particular domain and to a database describing the contents of individual documents in terms of these topics. This paper, then, focuses on the two central concepts behind EP-X: semantically based search and knowledge-based search tactics.

A self-administered questionnaire was completed by 145 Directory Assistance operators who used video display terminals (VDTs) to retrieve listings and by 105 control subjects who performed identical work except that they retrieved listings from printed paper records. The two groups exhibited few differences in their experience of work-related physical discomfort, in job satisfaction, or in their concerns about job security. Both groups were found to use eyeglasses and contact lenses to the same extent. VDT operators generally did not obtain special corrective lenses for work. The results show that replacing paper documents with VDTs need not adversely affect the comfort and morale of office workers.

Telephone operators served as their own controls in two field studies of advanced furniture designed for video display terminal (VDT) workstations. The advanced furniture was characterized by dimensions that were easily adjusted by users, in contrast with conventional furniture that provided either no adjustments or inconvenient adjustments that could only be made with difficulty. An eight-week study focused on advanced VDT tables, and a fiveweek study focused on advanced chairs. Four combinations of advanced and conventional workstation components were compared. Although on-the-job discomfort was reduced when either conventional component was replaced with an advanced component, the effect was far greater when the advanced table and the advanced chair were used together. The adjustments of the advanced furniture were reported to be easy to use, and the advanced furniture was rated more highly than the conventional furniture.

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