If two documents contain identical strings, the match alone cannot show which came first or which is the original. It establishes only that the text you compared matched under a particular representation and comparison rule—not who created it, when it was created, or how it reached you.
What an identical-string match establishes
A string comparison answers a limited question: do these text sequences count as matching under the chosen rules? The answer depends on what text was extracted, how characters were represented, and whether the comparison applied case folding or Unicode normalization. The W3C’s Character Model for the World Wide Web: String Matching explains those matching choices; it does not assign authorship, chronology, or provenance.
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So a match does not establish that one document was copied from the other, that either is the source, or that either was created first. Those conclusions require evidence beyond string equality.
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Why representation and comparison rules matter
Compare text in a common representation
Text can be encoded in different character encodings or represented by different character sequences. The W3C recommends converting text to a common Unicode representation before comparing it. A result should therefore be understood in light of how the compared text was represented and extracted—not as a judgment about the history of the files.
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Case folding and Unicode normalization can change the result
Matching rules may treat differences in capitalization or Unicode character forms as significant or insignificant. The W3C describes four options: no normalization, ASCII case folding, Unicode canonical case folding, and Unicode compatibility case folding. For identifiers and syntactic content, its default recommendation is no case folding and no Unicode normalization; alternatives are appropriate only in particular circumstances.
Compatibility normalization deserves particular care: it can change text meaning, appearance, and processing, potentially making a comparison too permissive. A match under that rule is not necessarily a match under a stricter rule. The comparison should state which rule was used.
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Be precise about what was compared
Matching extracted text is different from comparing entire files, and both are different from investigating a document’s history. A clear comparison should identify the text or content examined, how it was represented, and the matching rules applied. Without that context, “the documents match” can conceal important differences in what the comparison actually tested.
Even a well-specified text match establishes text identity only within its comparison scope. The W3C materials address string matching; they do not assess metadata, signatures, timestamps, version history, or custody. A string comparison therefore cannot settle which document is original.
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