Page 72 Concepts and similar pages

Concepts

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Index sequential file
Inverted file
Boolean search
Indexing
File structures
Probabilistic retrieval
Document clustering
Document representative
Sequential file
Retrieval effectiveness

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71 To unify the discussion of file structures we need some further concepts ...1 the K pointers are distinct;2 each non null K pointer in L gives the address of a record within L;3 there is a unique record in L not pointed to by any record containing K;it is called the beginning of the list;and 4 there is a unique record in L containing the null K pointer;it is the end of the list ...Hsiao and Harary state condition 2 slightly differently so that no two K lists have a record in common;this only appears to complicate things ...From our previous example:K 1 list:R 1,R 2,R 5 K 2 list:R 2,R 4 K 4 list:R 1,R 2,R 3 Finally,we need the definition of a directory of a file ...Ki,ni,hi,ai 1,ai 2,...We are now in a position to give a unified treatment of sequential files,inverted files,index sequential files and multi list files ...Sequential files A sequential file is the most primitive of all file structures ...The implementation of this file structure requires the use of asorting routine ...
73 arise if each record has just one unique keyword,or one unique attribute value ...img src Fig ...In the literature an index sequential file is usually thought of as a sequential file with a hierarchy of indices ...
77 is no K 3 list,the field reserved for its pointer could well have been omitted ...The multi list is designed to overcome the difficulties of updating an inverted file ...Cellular multi lists A further modification of the multi list is inspired by the fact that many storage media are divided into pages,which can be retrieved one at a time ...At this point the full power of the notation introduced before comes into play ...Ki,ni,hi,ai 1,...where the hi have beenpicked to ensure that a Ki list does not cross a page boundary ...Ring structures A ring is simply a linear list that closes upon itself ...