Text-classification system and method

An automated system for classifying a target document in the form of a digitally encoded text as belonging to one or more of a plurality of different classes comprising

• (1) a computer,
• (2) accessible by said computer, a database of word records, where each record includes text identifiers of the library texts that contain that word, associated library and classification identifiers for each text, and optionally, one or more selectivity values for each word, where the selectivity value of a term in a library of texts in a field is related to the frequency of occurrence of that term in said library, relative to the frequency of occurrence of the same term in one or more other libraries of texts in one or more other fields, respectively,
• (3) a computer readable code which is operable, under the control of said computer, to perform the steps of
• (a) for each of a plurality of terms composed of non-generic words and, optionally, proximately arranged word groups characterizing the target document, selecting that term as a descriptive term if the term has an above-threshold selectivity value in at least one library of texts in a field, by (i) accessing said database and (ii) calculating or recording from the database, the selectivity value associated with that term,
• (b) determining for each of the plurality of library texts, a match score related to the number of descriptive terms present in or derived from that text that match those in the target document,
• (c) selecting one or more of the library texts having the highest match scores,
• (d) recording the one or more classification identifiers associated with the one or more library texts having the highest match scores, and
• (e) associating the one or more classification identifiers from step (d) with the target document, thereby to classify the target document as belonging to at least class represented by the classification identifiers from step (d).

Computer readable code for use with an electronic computer and a database word records in classifying a target document in the form of a digitally encoded text as belonging to one or more of a plurality of different classes, where each record in the word records database includes text identifiers of the library texts that contain that word, an associated library identifier for each text, an associated classification identifier for each text, and optionally, one or more selectivity values for each word, where the selectivity value of a term in a library of texts in a field is related to the frequency of occurrence of that term in said library, relative to the frequency of occurrence of the same term in one or more other libraries of texts in one or more other fields, respectively, said code being operable, under the control of said computer, to perform the steps of

• (a) for each of a plurality of terms composed of non-generic words and, optionally, proximately arranged word groups characterizing the target document, selecting that term as a descriptive term if the term has an above-threshold selectivity value in at least one library of texts in a field, by (i) accessing said database and (ii) calculating or recording from the database, the selectivity value associated with that term,
• (b) determining for each of the plurality of library texts, a match score related to the number of descriptive terms present in or derived from that text that match those in the target document,
• (c) selecting one or more of the library texts having the highest match scores,
• (d) recording the one or more classification identifiers associated with the one or more library texts having the highest match scores, and
• (e) associating the one or more classification identifiers from step (d) with the target document, thereby to classify the target document as belonging to at least one class represented by the classification identifiers from step (d).