The calculation is optimized to identify the common
largest substring.
The return value is an array of the following format:
array(
array( diff-type => substring ),
array(...)
)
whereby diff-type can be one of:
-1 = deletion
0 = common substring
1 = addition
/**
* @covers PKPString::diff
*/
public function testDiff()
{
// Test two strings that have common substrings.
$originalString = 'The original string.';
$editedString = 'The edited original.';
$expectedDiff = array(array(0 => 'The'), array(1 => ' edited'), array(0 => ' original'), array(-1 => ' string'), array(0 => '.'));
$resultDiff = PKPString::diff($originalString, $editedString);
self::assertEquals($expectedDiff, $resultDiff);
// Test two completely different strings.
$originalString = 'abc';
$editedString = 'def';
$expectedDiff = array(array(-1 => 'abc'), array(1 => 'def'));
$resultDiff = PKPString::diff($originalString, $editedString);
self::assertEquals($expectedDiff, $resultDiff);
// A more realistic example from the citation editor use case
$originalString = 'Willinsky, B. (2006). The access principle: The case for open acces to research and scholarship. Cambridge, MA: MIT Press.';
$editedString = 'Willinsky, J. (2006). The access principle: The case for open access to research and scholarship. Cambridge, MA: MIT Press.';
$expectedDiff = array(array(0 => 'Willinsky, '), array(-1 => 'B'), array(1 => 'J'), array(0 => '. (2006). The access principle: The case for open acce'), array(1 => 's'), array(0 => 's to research and scholarship. Cambridge, MA: MIT Press.'));
$resultDiff = PKPString::diff($originalString, $editedString);
self::assertEquals($expectedDiff, $resultDiff);
}
/**
* Derive a confidence score calculated as the similarity of the
* original raw citation and the citation text generated from the
* citation description.
* @param $metadataDescription MetadataDescription
* @return integer filter confidence score
*/
function _filterConfidenceScore(&$metadataDescription)
{
// Retrieve the original plain text citation.
$originalCitation = $this->getOriginalRawCitation();
// Generate the formatted citation output from the description.
$citationOutputFilter =& $this->getCitationOutputFilter();
$generatedCitation = $citationOutputFilter->execute($metadataDescription);
// Strip formatting and the Google Scholar tag so that we get a plain
// text string that is comparable with the raw citation.
$generatedCitation = trim(str_replace(GOOGLE_SCHOLAR_TAG, '', strip_tags($generatedCitation)));
// Compare the original to the generated citation.
$citationDiff = PKPString::diff($originalCitation, $generatedCitation);
// Calculate similarity as the number of deleted characters in relation to the
// number of characters in the original citation. This intentionally excludes
// additions as these can represent useful data like a DOI or an external link.
$deletedCharacters = 0;
foreach ($citationDiff as $diffPart) {
// Identify deletions.
if (key($diffPart) == -1) {
$deletedCharacters += PKPString::strlen(current($diffPart));
}
}
$originalCharacters = PKPString::strlen($originalCitation);
$partOfCommonCharacters = ($originalCharacters - $deletedCharacters) / $originalCharacters;
$filterConfidenceScore = (int) round(min($partOfCommonCharacters * 100, 100));
return $filterConfidenceScore;
}
