An information processing device includes a keyword acquiring unit configured to acquire a plurality of primary keyword and secondary keyword groups; a classifying unit configured to classify each of the plurality of secondary keywords by a plurality of topics; an estimating unit configured to estimate whether or not each primary keyword in the plurality of groups is a related keyword related to any topic having a classified secondary keyword or a mixed keyword unrelated to any of the topics; and an assigning unit configured to preferentially assign a primary keyword estimated to be a related keyword to a topic having a classified secondary keyword in the same group, and assigning a primary keyword estimated to be a mixed keyword to any of all the topics given for classification.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. An information processing method executed by a computer, the method comprising: acquiring a plurality of primary keyword and secondary keyword groups; classifying each of the plurality of secondary keywords by a plurality of topics; estimating whether or not each primary keyword in the plurality of groups is a related keyword related to any topic having a classified secondary keyword or a mixed keyword unrelated to any of the topics; and assigning a primary keyword estimated to be a related keyword to a topic having a classified secondary keyword in the same group, and assigning a primary keyword estimated to be a mixed keyword to any of the topics for classification. 2. The method of claim 1, further comprising: determining a topic to assign a primary keyword estimated to be a related keyword on the basis of the proportion of secondary keywords classified by each topic in the same group; and determining a topic to assign a primary keyword estimated to be a mixed keyword irrespective of the proportions. 3. The method of claim 1, further comprising acquiring primary document information including more than one primary keyword, and secondary document information including more than one secondary keyword created by a user. 4. The method of claim 3, further comprising estimating whether or not a primary keyword is a related keyword or a mixed keyword on the basis of primary topics having assigned primary keywords and secondary topics having assigned secondary keywords. 5. The method of claim 4, further comprising: acquiring a primary topic of the primary keyword; calculating the extent of the topic match being the proportion of secondary topics assigned to one or more secondary keywords that are the same as the primary topic; acquiring the mixed keyword ratio or the ratio of primary keywords estimated to be mixed keywords among primary keywords included in primary document information from all users; and calculating the mixed keyword probability of the primary keyword being a mixed keyword on the basis of the extent of the topic match and the mixed keyword ratio. 6. The method of claim 5, further comprising determining whether a primary keyword is a related keyword or a mixed keyword on the basis of the mixed keyword probability. 7. The method of claim 4, further comprising calculating the likelihood Ψkt of the tth primary keyword t, wherein t is an integer >1, appearing in the kth topic, wherein k is a predetermined integer >1, in all sets of primary document information from a user. 8. The method of claim 7, further comprising generating the probability θdk of the kth topic k in each set of secondary document information d, wherein d>1 but less than the total number of sets of secondary document information being generated. 9. The method of claim 8, further comprising calculating a primary keyword generation probability P(t|d, D) of a primary keyword t being assigned to a single set of secondary document information d by totaling the θdkΨkt of each topic k in the set of secondary document data d.