7. A method for generating a ‘snapshot’ of a learning object, comprising: receiving a target object corresponding to a category, wherein the target object comprises a plurality of sentences and multimedia data, and the sentences comprise at least one target object keyword; receiving a user identification number; providing a learning object database, comprising: a plurality of learning objects, wherein each of the learning objects corresponds to at least one category and comprises at least one learning object keyword; and a user's historical learning record comprising a track record of learning objects used corresponding to the user identification number; selecting at least one of the sentences of the target object as a preview sentence according to the user's historical learning record corresponding to the user identification number; selecting one of the multimedia data of the target object as a preview multimedia data, wherein the selected multimedia data is highly related to the selected sentence; generating a ‘snapshot’ of the target object by combining the preview sentence and the preview multimedia data, and displaying the ‘snapshot’; receiving a user keyword input by a user; calculating the amount of information contained in the plurality of sentences of the target object, further comprises: calculating a relationship matrix of the plurality of sentences in the target object, wherein the relationship matrix comprises a relationship value for each pair of the plurality of sentences; and calculating a sum of the relationship values of each of the plurality of sentences and other sentences of the plurality of sentences as a value specifying the amount of information thereof; selecting at least one pertinent keyword relating to the target object from the plurality of learning objects according to the user's historical learning record corresponding to the user identification number; and selecting the sentence, among the plurality of sentences, that contain the largest amount of information and contain the user keyword or the pertinent keyword as the preview sentence.
8. The method for generating a ‘snapshot’ of a learning object claim 7 , wherein the relationship value of each pair of the plurality of sentences is calculated according to the following equation: R ⁡ ( i , j ) = ( Ui ⋂ Uj ) × 2 Ui ⋃ Uj , wherein Ui represents binary terms in the sentence Si of the target object, Uj represents binary terms in the sentence Sj of the target object, Ui∪Uj represents a total number of the binary terms of Ui and Uj, and Ui∩Uj represents a number of binary terms appearing in both Ui and Uj.