ISR11 Operating Instructions for the SMART Text Processing and Document Retrieval System chapter M. E. Lesk Harvard University Gerard Salton Use, reproduction, or publication, in whole or in part, is permitted for any purpose of the United States Government. ii-i4 concepts which co-occur with similar concepts. For example, if one is see[OCRerr]ng to identify that 1'aeroplane'1 and "aircraft't represent the same concept, one might deduce this not from the fact that they co-occur in the same document, but that they each separately co-occur with words such as "fusilage", "propeller", "aileron11, and the like. The SMART system m[OCRerr]kes provision for iterated concept-concept correlation to any depth. The specifications affecting this procedure are as follows: CONOON n the nun[OCRerr]ber "n" is the nun[OCRerr]ber of iterations of the concept-concept correlation process. "CONCON 1" specifies simple first-order correlation; [OCRerr]DECC a a is either "COS" or "OVLAP" to specify cosine or over- lap correlation for the first concept-concept correlation; [OCRerr]D[OCRerr]C a a is either COS or OVLAP to specify the correlation mode for concept-concept correlations after the first corre- lation, i.e., for the second and following iterations; CUTCC x x is a number between 0 and 1 (0.6 is typical) to specify the cutoff for the first concept-concept correlation; CUT2C x x is a nuzi[OCRerr]ber between 0 and 1 specifying the cutoff for correlations after the first; CO[OCRerr][OCRerr]IN n n specifies the lowest concept number which will be correlated. This specification is to be used primarily with null dictionaries prepared by THES (see part 6.1) in which the concepts are arranged by frequency, thus m[OCRerr]aing it possible to specify the lowest frequency word to be correlated; CONMAX n n specifies the highest concept number which will be corre- lated. CO[OCRerr][OCRerr]IN and CONMAX are used because the statistical procedures are not accurate for words which occur either very rarely or very frequently;