SpeedRead: A Fast Named Entity Recognition Pipeline
Table 7: Confusion Matrix of the POS tags assigned by SpeedRead over the words of sections 22-24 of PTB. O represents all the other not mentioned tags.
['[0pt][l]RefTest', 'DT', 'IN', 'JJ', 'NN', 'NNP', 'NNPS', 'NNS', 'RB', 'VBD', 'VBG', 'O']
Proper nouns are the second source of errors as most of the capitalized words will be mistakenly tagged as proper nouns while they are either adjectives or nouns. Such errors are the result of the weak logic implemented in the backoff tagger in SpeedRead, where regular expressions are applied in sequence returning the first match. Other types of errors are adverbs (RB) and propositions (IN). These errors are mainly because of the ambiguity of the functional words. Functional words need deeper understanding of discourse, semantic and syntactic nature of the text. Taking into consideration the contexts around the words improves the accuracy of tagging. However, trigrams are still small to be considered sufficient context for resolving all the ambiguities.