Some Mathematics of Information Storage and Retrieval.

Fuente: ERIC Institute of Education Sciences

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Bibliographic Details
Main Author:	Sammon, John W., Jr.
Format:	Recurso educativo Open Access
Language:	en
Published:	1968
Subjects:	Algebra Indexing Information Retrieval Information Storage Mathematical Applications Mathematical Models Mathematics Probability Statistical Analysis
Online Access:	Acceder al recurso
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author	Sammon, John W., Jr.
author_facet	Sammon, John W., Jr. Sammon, John W., Jr.
collection	Education Resources Information Center
contents	Some Mathematics of Information Storage and Retrieval. Sammon, John W., Jr. Algebra Indexing Information Retrieval Information Storage Mathematical Applications Mathematical Models Mathematics Probability Statistical Analysis This report explains the following mathematical techniques which may be used for relating search requests to documents contained in a library: (1) Boolean Algebraic Retrieval, (2) Linear Statistical Retrieval, (3) Statistical Association Techniques for expanding a query and/or for expanding the set of retrieval documents, (4) Vector Space representation of the retrieval process, and (5) Discriminant Analysis Techniques. (RP)
format	Recurso educativo Open Access
id	eric_ED026084
institution	ERIC Institute of Education Sciences
language	en
publishDate	1968
record_format	eric
spellingShingle	Some Mathematics of Information Storage and Retrieval. Sammon, John W., Jr. Algebra Indexing Information Retrieval Information Storage Mathematical Applications Mathematical Models Mathematics Probability Statistical Analysis Some Mathematics of Information Storage and Retrieval. Sammon, John W., Jr. Algebra Indexing Information Retrieval Information Storage Mathematical Applications Mathematical Models Mathematics Probability Statistical Analysis This report explains the following mathematical techniques which may be used for relating search requests to documents contained in a library: (1) Boolean Algebraic Retrieval, (2) Linear Statistical Retrieval, (3) Statistical Association Techniques for expanding a query and/or for expanding the set of retrieval documents, (4) Vector Space representation of the retrieval process, and (5) Discriminant Analysis Techniques. (RP)
title	Some Mathematics of Information Storage and Retrieval.
topic	Algebra Indexing Information Retrieval Information Storage Mathematical Applications Mathematical Models Mathematics Probability Statistical Analysis
url	https://eric.ed.gov/?id=ED026084

if (filemtime($filename) + $maxlifetime < time()) { unlink($filename); $count++; } } return $count; } /** * A function that is called internally when session data is to be saved. * * @param string $sessId The current session ID * @param string $data The session data to write * * @return bool */ protected function saveSession($sessId, $data): bool { $sessFile = $this->path . '/sess_' . $sessId; if ($handle = fopen($sessFile, 'w')) { $return = false; // Lock the file for exclusive access to avoid issues with multiple // processes writing session simultaneously: if (flock($handle, LOCK_EX)) { $return = fwrite($handle, $data); // Make sure that there's no trailing data by truncating the file to // the correct length: ftruncate($handle, strlen($data)); fflush($handle); flock($handle, LOCK_UN); } fclose($handle); if ($return !== false) { return true; } } // If we got this far, something went wrong with the file output... // It is tempting to throw an exception here, but this code is called // outside of the context of exception handling, so all we can do is // echo a message.

// Anecdotal testing Today and Yesterday seems to indicate destroy() // is called by the garbage collector and everything is good. // Something to keep in mind though. return 0; } /** * Write function that is called when session data is to be saved. * * @param string $sessId The current session ID * @param string $data The session data to write * * @return bool */ public function write($sessId, $data): bool { if ($this->writesDisabled) { return true; } return $this->saveSession($sessId, $data); } /** * A function that is called internally when session data is to be saved. * * @param string $sessId The current session ID * @param string $data The session data to write * * @return bool */ abstract protected function saveSession($sessId, $data): bool; }

* * @return void */ public function writeClose() { // The assumption is that we're using PHP's ext/session. // session_write_close() will actually overwrite $_SESSION with an // empty array on completion -- which leads to a mismatch between what // is in the storage object and $_SESSION. To get around this, we // temporarily reset $_SESSION to an array, and then re-link it to // the storage object. // // Additionally, while you _can_ write to $_SESSION following a // session_write_close() operation, no changes made to it will be // flushed to the session handler. As such, we now mark the storage // object isImmutable. $storage = $this->getStorage(); if (! $storage->isImmutable()) { $_SESSION = $storage->toArray(true); session_write_close(); $storage->fromArray($_SESSION); $storage->markImmutable(); } } /** * Attempt to set the session name * * If the session has already been started, or if the name provided fails * validation, an exception will be raised. * * @param string $name * @return SessionManager * @throws Exception\InvalidArgumentException */ public function setName($name) { if ($this->sessionExists()) { throw new Exception\InvalidArgumentException( 'Cannot set session name after a session has already started'

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