ISR11 Design Consideration for Time Shared Automatic Documentation Centers 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. X-12 dictionary is brought in from disk or data cell. If the disk is used for the dictionary, it will take about 0.075 sec. for access plus a few milliseconds for the search. If the data cell is used, perhaps 0.5 seconds per reference will be necessary. The lookup procedure should be completed in one second or less. In practice, if the full dictionary is referred to very frequently, it may be desirable to increase the size of the special dictionary to 5000 words or more (this should be possible with a 360/67 computer). If the dictionary is stored on disks this should not be necessary, since ten disk references could be made before the wait becomes excessive. It is unlikely that more than ten references per request would be required, since most requests will contain about ten significant words. Access to the data cell, on the other hand, is slower, and a larger internal dictionary might be needed if a data cell were used for the dictionery storage. The present SMART system for dictionary storage and search would probably be useable in the new system. Some economies in dictionary storage, however, would probably be made in an effort to save memory space. The total dictionary size should be of the order Qf l0[OCRerr] bits. Note that if the entire dictionary has to be read into memory, the lookup process 6 would take at least ten seconds, even at high read rate of 10 bits per second. If more than one request is submitted at the same time, it might be possible to save time if these requests were to require the same sections of the expanded dictionary to complete the lookup. It is debatable, however, whether the time saved in this way is worth the progra=ming effort involved, considering the improbability of two users happening to &ubmit