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have been clustered as clustered files
...Some of the work that has been largely ignored in this chapter,but which is nevertheless of importance when considering the implementation of a file structure,is concerned directly with the physical organisation of a storage device in terms of block sizes,etc
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The structure of the book The introduction presents some basic background material,demarcates the subject and discusses loosely some of the problems in IR
...The two major chapters are those dealing with automatic classification and evaluation
...Outline Chapter 2:Automatic Text Analysis contains a straightforward discussion of how the text of a document is represented inside a computer
...Chapter 3:Automatic Classification looks at automatic classification methods in general and then takes a deeper look at the use of these methods in information retrieval
...Chapter 4:File Structures here we try and discuss file structures from the point of view of someone primarily interested in information retrieval
...Chapter 5:Search Strategies gives an account of some search strategies when applied to document collections structured in different ways
...Chapter 6:Probabilistic Retrieval describes a formal model for enhancing retrieval effectiveness by using sample information about the |
| 67 |
packing the nodes of the tree on the disk given the access characteristics of the disk
...The work on data bases has been very much concerned with a concept called data independence
...There is a school of thought that says that says that applications in library automation and information retrieval should follow this path as well [6,7]...Nevertheless,it is worth taking seriously the trend away from user knowledge of file structures,a trend that has been stimulated considerably by attempts to construct a theory of data [8,9],which has become known as the relational model
...A second approach is the hierarchical approach
...The third approach is the network approach associated with the proposals by the Data Base Task Group of CODASYL
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| 60 |
differences in the scale and in the use to which a classification structure is to be put
...In the case of scale,the size of the problem in IR is invariably such that for cluster methods based on similarity matrices it becomes impossible to store the entire similarity matrix,let alone allow random access to its elements
...When a classification is to be used in IR,it affects the design of the algorithm to the extent that a classification will be represented by a file structure which is 1 easily updated;2 easily searched;and 3 reasonably compact
...Only 3 needs some further comment
...Conclusion Let me briefly summarise the logical structure of this chapter
...This chapter ended on a rather practical note
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| 68 |
are linked into a network in which any given link between two items exists because it satisfies some condition on the attributes of those items,for example,they share an attribute
...The whole field of data base structures is still very much in a state of flux
...Lurking in the background of any discussion of file structures nowadays is always the question whether data base technology will overtake all
...A language for describing file structures Like all subjects in computer science the terminology of file structures has evolved higgledy piggledy without much concern for consistency,ambiguity,or whether it was possible to make the kind of distinctions that were important
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