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| 8 |
The process may involve structuring the information in some appropriate way,such as classifying it
...Finally,we come to the output,which is usually a set of citations or document numbers
...IR in perspective This section is not meant to constitute an attempt at an exhaustive and complete account of the historical development of IR
...Since the emphasis in this book is on a particular approach to document representation,I shall restrict myself here to a few remarks about its history
...At this point,it may be convenient to elaborate on the use of keyword
...The use of statistical information about distributions of words in documents was further exploited by Maron and Kuhns [11]who obtained statistical associations between keywords
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| 10 |
In the past there has been much debate about the validity of evaluations based on relevance judgments provided by erring human beings
...Effectiveness and efficiency Much of the research and development in information retrieval is aimed at improving the effectiveness and efficiency of retrieval
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| 9 |
Sparck Jones has carried on this work using measures of association between keywords based on their frequency of co occurrence that is,the frequency with which any two keywords occur together in the same document
...The term information structure for want of better words covers specifically a logical organisation of information,such as document representatives,for the purpose of information retrieval
...The organisation of these files is produced by an automatic classification method
...Evaluation of retrieval systems has proved extremely difficult
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| 146 |
There has been much debate in the past as to whether precision and recall are in fact the appropriate quantities to use as measures of effectiveness
...1 the most commonly used pair;2 fairly well understood quantities
...The final question How to evaluate?has a large technical answer
...Before proceeding to the technical details relating to the measurement of effectiveness it is as well to examine more closely the concept of relevance which underlies it
...Relevance Relevance is a subjective notion
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| 148 |
relevant to an information need if and only if it contains at least one sentence which is relevant to that need
...Earlier on I stated that this notion of relevance was only of limited use at the moment
...Saracevic [8]has summarised some of the more recent work on probabilistic interpretations of relevance
...Precision and recall,and others We now leave the speculations about relevance and return to the promised detailed discussion of the measurement of effectiveness
...It is helpful at this point to introduce the famous contingency table which is not really a contingency table at all
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| 145 |
automatic and interactive retrieval system?Studies to gauge this are going on but results are hard to interpret
...It should be apparent now that in evaluating an information retrieval system we are mainly concerned with providing data so that users can make a decision as to 1 whether they want such a system social question and 2 whether it will be worth it
...The second question what to evaluate?boils down to what can we measure that will reflect the ability of the system to satisfy the user
...1 The coverage of the collection,that is,the extent to which the system includes relevant matter;2 the time lag,that is,the average interval between the time the search request is made and the time an answer is given;3 the form of presentation of the output;4 the effort involved on the part of the user in obtaining answers to his search requests;5 the recall of the system,that is,the proportion of relevant material actually retrieved in answer to a search request;6 the precision of the system,that is,the proportion of retrieved material that is actually relevant
...It is claimed that 1 4 are readily assessed
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| 168 |
Foundation Problems of measurement have arisen in physics,psychology,and more recently,the social sciences
...The problems of measurement in information retrieval differ from those encountered in the physical sciences in one important aspect
...The next three sections are substantially the same as those appearing in my paper:Foundations of evaluation,Journal of Documentation,30,365 373 1974
...no reason why we cannot postulate a particular ordering,or,to put it more mildly,why we can not show that a certain model for the measurement of effectiveness has acceptable properties
...1 all properties ascribed are consistent;2 they bring out into the open all the assumptions made in measuring effectiveness;3 each property has an acceptable interpretation;4 the model leads to a plausible measure of effectiveness
...It is as well to point out here that it does not lead to a uniquemeasure,but it does show that certain classes of measures can beregarded as being equivalent
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| 30 |
In practice,one seeks some sort of optimal trade off between representation and discrimination
...The emphasis on representation leads to what one might call a document orientation:that is,a total preoccupation with modelling what the document is about
...This point of view is also adopted by those concerned with defining a concept of information,they assume that once this notion is properly explicated a document can be represented by the information it contains [37]...The emphasis on discrimination leads to a query orientation
...Automatic keyword classification Many automatic retrieval systems rely on thesauri to modify queries and document representatives to improve the chance of retrieving relevant documents
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| 5 |
frequency of occurrence and co occurrence of index terms in the relevant and non relevant documents
...Chapter 7:Evaluation here I give a traditional view of the measurement of effectiveness followed by an explanation of some of the more promising attempts at improving the art
...Chapter 8:The Future contains some speculation about the future of IR and tries to pinpoint some areas of research where further work is desperately needed
...Information retrieval Since the 1940 s the problem of information storage and retrieval has attracted increasing attention
...In principle,information storage and retrieval is simple
...When high speed computers became available for non numerical work,many thought that a computer would be able to read an entire document collection to extract the relevant documents
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