Research and Advances

Experimental evaluation of information retrieval through a teletypewriter

Experiments designed to evaluate the capabilities of mechanized information retrieval systems, with emphasis on interactive (man-machine) language and on some of the mechanical and psychological limitations in their design, were conducted at the Moore School Information Systems Laboratory. The basic assumption of the research is that an information retrieval system that provides for man-machine dialogue at a remote inquiry terminal should provide a searcher with many of the tools which would be available to him were he actually performing his search at a library or repository of documents. Factors involved in evaluation of such a system include ease of use, learning time, and effectiveness of actual retrieval. Three experiments and the conclusions resulting from them are detailed.

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Research and Advances

n-dimensional codes for detecting and correcting multiple errors0

The paper introduces a new family of codes for detecting and correcting multiple errors in a binary-coded message. The message itself is arranged (conceptually) into a multidimensional rectangular array. The processes of encoding and error detection are based upon parity evaluations along prescribed dimensions of the array. Effectiveness of the codes is increased by introducing a “system check bit”, which is essentially a parity check on the other parity bits. Only three-dimensional codes are discussed in this paper, with parity evaluations along the horizontal, the vertical, and one main diagonal. However, the family of codes is not restricted to three dimensions, as evidenced by the discussion by Minnick and Ashenhurst on a similar multidimensional single-bit selection plan used for another purpose [6]. A four-dimensional code, correcting three and detecting four errors, has been developed; the extension to higher-dimensional codes with greater correction power is straightforward.

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