A system and method are provided to monetize content by redacting the content with machine learning algorithms. This invention increases the conversion rate of website surfers to paid customers. Extracted texts of the content are tokenized and then scored with normalized value [0, 1] to measure their significance. Intra-token, inter-token, extra-token, and tagged token features are used to characterize each individual token. Scores of sentences, paragraphs, sections, and even chapters can be calculated with various methods based on the scores of tokens. Then, the content is redacted according to the calculated scores. Customers can view the redacted content for free. If interested, they can purchase the content and view the full, non-redacted version of the content. The present invention is useful in publication and monetization of digital contents such as e-books.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A computer-implemented method for redacting digital content in an online monetization process, the method comprising: extracting text information from the digital content; generating a plurality of tokens from the text information; calculating a token score for each token based on a plurality of feature values of the respective token, wherein the plurality of feature values comprise at least two of an intra-token feature value, an inter-token feature value, an extra-token feature value, and a tagged-token feature value; and redacting a portion of the digital content based on the token scores. 2. The computer-implemented method of claim 1, wherein the digital content comprises an electronic document. 3. The computer-implemented method of claim 2, wherein the token score for each token is normalized into [0, 1], and wherein the redacting step comprises: comparing the token score of each token with a predetermined threshold value; and redacting the respective token if the token score of the token is greater than the predetermined threshold value. 4. The computer-implemented method of claim 3, wherein the intra-token feature value of each token is determined based on entropies of letters in the respective token, the inter-token feature value of each token is determined based on an estimated importance of the respective token in a corresponding context calculated by an automatic keyword extraction tool, the extra-token feature value of each token is determined based on whether the respective token is in a first set of preselected tokens, and the tagged-token feature value of each token is determined based on whether the respective token is in a second set of preselected tokens. 5. The computer-implemented method of claim 4, wherein the first set of preselected tokens comprises a plurality of words of general public interest. 6. The computer-implemented method of claim 4, wherein the second set of preselected tokens comprises a plurality of words selected by a content provider of the digital content. 7. The computer-implemented method of claim 1, further comprising: calculating a score for each of a plurality of language elements of the text information based on the token scores; and normalizing the score of each language element into [0, 1]. 8. The computer-implemented method of claim 7, wherein the redacting step comprises: comparing the normalized score of each language element with a predetermined threshold value; and redacting the respective language element if the normalized score of the language element is greater than the predetermined threshold value. 9. The computer-implemented method of claim 8, wherein the plurality of language elements is one of a plurality of sentences, a plurality of paragraphs, a plurality of sections, and a plurality of chapters. 10. The computer-implemented method of claim 1, further comprising calculating a percentile for each token based on the respective token's token score, and wherein the redacting step comprises redacting the respective token if the percentile of the token is greater than a predetermined threshold. 11. A system for redacting digital content, the system comprising: a memory for storing instructions; and a processor which, upon executing the instructions, performs a process comprising: extracting text information from the digital content; generating a plurality of tokens from the text information; calculating a token score for each token based on a plurality of feature values of the respective token, wherein the plurality of feature values comprise at least two of an intra-token feature value, an inter-token feature value, an extra-token feature value, and a tagged-token feature value; and redacting a portion of the digital content based on the token scores. 12. The system of claim 11, wherein the calculating step further comprises normalizing the token score for each token into [0, 1], and wherein the redacting step comprises: comparing the normalized token score of each token with a predetermined threshold value; and redacting the respective token if the normalized token score of the token is greater than the predetermined threshold value. 13. The system of claim 12, wherein the intra-token feature value of each token is determined based on entropies of all letters in the respective token, the inter-token feature value of each token is determined based on an estimated importance of the respective token in a corresponding context calculated by an automatic keyword extraction tool, the extra-token feature value of each token is determined based on whether the respective token is in a first set of preselected tokens, and the tagged-token feature value of each token is determined based on whether the respective token is in a second set of preselected tokens. 14. The system of claim 13, wherein the first set of preselected tokens comprises a first plurality of words of general public interest, and the second set of preselected tokens comprises a second plurality of words selected by a content provider of the content. 15. The system of claim 11, wherein the process further comprises calculating a score for each of a plurality of language elements of the text information based on the token scores, and wherein the redacting step comprises redacting the portion of the content based on the scores of the plurality of language elements. 16. The system of claim 15, wherein the plurality of language elements is one of a plurality of sentences, a plurality of paragraphs, a plurality of sections, and a plurality of chapters. 17. The system of claim 11, wherein the process further comprises calculating a percentile for each of a plurality of sentences of the text information based on the token scores, and wherein said redacting step comprises redacting the respective sentence if the percentile of the sentence is greater than a predetermined threshold. 18. A computer-readable medium having computer-executable instructions stored thereon which, when executed by a computer, cause the computer to: generate a plurality of tokens from an electronic document; calculate a token score for each token based on a plurality of feature values of the respective token, wherein the plurality of feature values comprise at least two of an intra-token feature value, an inter-token feature value, an extra-token feature value, and a tagged-token feature value, and wherein the intra-token feature value of each token is determined based on entropies of all letters in the respective token, the inter-token feature value of each token is determined based on an estimated importance of the respective token in a corresponding context calculated by an automatic keyword extraction tool, the extra-token feature value of each token is determined based on whether the respective token is in a first set of preselected tokens, and the tagged-token feature value of each token is determined based on whether the respective token is in a second set of preselected tokens; and redact parts of the electronic document based on the token scores. 19. The computer-readable medium of claim 18, wherein said redact step comprises: determine a percentage value based on a customer's payment amount over a full payment amount needed for viewing the whole portion of the electronic document; calculate a percentile for each token based on the respective token's token score; and redacting the respective token if the percentile of the token is greater than the percentage value. 20. The computer-readable medium of claim 18, wherein said redact step comprises replace the parts of the electronic document with empty block fillers.