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| 6 |
language input and storage more feasible
...The reader will have noticed that already,the idea of relevance has slipped into the discussion
...Intellectually it is possible for a human to establish the relevance of a document to a query
...An information retrieval system Let me illustrate by means of a black box what a typical IR system would look like
...Starting with the input side of things
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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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| 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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| 189 |
The time is ripe for another attempt at using natural language to represent documents inside a computer
...It has never been assumed that a retrieval system should attempt to understand the content of a document
...Such an approach would make feedback a major tool
...Future developments Much of the work in IR has suffered from the difficulty of comparing retrieval results
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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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| 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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| 144 |
Seven EVALUATION Introduction Much effort and research has gone into solving the problem of evaluation of information retrieval systems
...In a book of this nature it will be impossible to cover all work to date about evaluation
...To put the problem of evaluation in perspective let me pose three questions:1 Why evaluate?2 What to evaluate?3 How to evaluate?The answers to these questions pretty well cover the whole field of evaluation
...The answer to the first question is mainly a social and economic one
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The lesson that is to be learnt is that should new research get underway it will be very important to have a suitable data base ready
...Information retrieval systems are likely to play an every increasing part in the community
...One major recent development is that computers and data bases are becoming linked into A study recommending the provision of such an experimental test bed has recently been completed,see Sparck Jones and van Rijsbergen,Information retrieval test collections,Journal of Documentation,32,59 75 1976
...networks
...By extending the user population to include the non specialist,it is likely that an IR system will be expected to provide not just a citation,but a display of the text,or part of it,and perhaps answer simple questions about the retrieved documents
...To bring all this about the document retrieval system will have to be interfaced and integrated with data retrieval systems,to give access to facts related to those in the documents
...Another example can be found in the context of computer aided instruction,where it is clearly a good idea to give a student access to a document retrieval system which will provide him with further reading on a topic of his immediate interest
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| 114 |
the system to its user will be the best that is obtainable on the basis of those data
...Of course this principle raises many questions as to the acceptability of the assumptions
...The probability ranking principle assumes that we can calculate P relevance document,not only that,it assumes that we can do it accurately
...So returning now to the immediate problem which is to calculate,or estimate,P relevance document
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