8. An information analysis method using a plurality of linguistic expressions as an analysis target, the information analysis method comprising: (a) a step of extracting time information included in each of a plurality of electronic documents including at least any one of the plurality of linguistic expressions and a relationship between the electronic documents in the plurality of electronic documents from the plurality of electronic documents; (b) a step of detecting a link between one linguistic expression and another linguistic expression in the plurality of linguistic expressions and an appearance time of the link based on the time information and the relationship between the electronic documents that are extracted in step (a), and generating link information specifying the detected link and the appearance time of the link; and (c) a step of specifying the number of appearances of links between the one linguistic expression and the other linguistic expression and an appearance time of each link based on the link information generated in step (b), and calculating a correlation value between the one linguistic expression and the other linguistic expression by using the number of appearances of the link and the appearance time of each link, the calculation of the correlation value being made by using a function that increases depending on a difference between first appearance time of one link and second appearance time of another link, wherein each step is implemented by a CPU.
8. An information analysis method using a plurality of linguistic expressions as an analysis target, the information analysis method comprising: (a) a step of extracting time information included in each of a plurality of electronic documents including at least any one of the plurality of linguistic expressions and a relationship between the electronic documents in the plurality of electronic documents from the plurality of electronic documents; (b) a step of detecting a link between one linguistic expression and another linguistic expression in the plurality of linguistic expressions and an appearance time of the link based on the time information and the relationship between the electronic documents that are extracted in step (a), and generating link information specifying the detected link and the appearance time of the link; and (c) a step of specifying the number of appearances of links between the one linguistic expression and the other linguistic expression and an appearance time of each link based on the link information generated in step (b), and calculating a correlation value between the one linguistic expression and the other linguistic expression by using the number of appearances of the link and the appearance time of each link, the calculation of the correlation value being made by using a function that increases depending on a difference between first appearance time of one link and second appearance time of another link, wherein each step is implemented by a CPU. 14. The information analysis method according to claim 8 , further comprising: (d) a step of receiving a first linguistic expression as an analysis target; and (e) a step of generating a second linguistic expression relevant to the first linguistic expression, wherein the plurality of linguistic expressions are the first linguistic expression and the second linguistic expression, the one linguistic expression is the first linguistic expression, and the another linguistic expression is the second linguistic expression.