2. The computer program product according to claim 1 , wherein calculating the total importance of each of the plurality of electronic documents includes calculating the total importance of each of the electronic documents, by sequentially applying (a) to (d) to each of a plurality of pairs of the chained electronic documents, starting from a pair of the start electronic document and an electronic document that the start electronic document references toward the terminal electronic document along the chain.
1. A computer program product comprising: a non-transitory computer useable storage medium including a computer readable program, wherein the computer readable program when executed on a computer causes the computer to function as a system for calculating total importance of each of electronic documents, based on (i) a plurality of electronic documents chained to each other in a relation of referencing, from a start electronic document which is not referenced by any other electronic document to a terminal electronic document which does not reference any other document, (ii)information on relation of referencing and being referenced, (iii) an important phrase, and (iv) a response coefficient determining phrase, (i) through (iv) being stored in a storage device, the computer program causing a computer to (a) calculate importance of a given electronic document among the plurality of electronic documents, on the basis of the degree of similarity between the important phrase and a phrase included in the given electronic document; (b) identify at least one second electronic document which references the given electronic document, on the basis of information referenced; (c) calculate a response coefficient against a first electronic document, on the basis of a degree of similarity between a phrase included in the second electronic document and the response coefficient determining phrase; (d) calculate the total importance of the given electronic document, based on importance unique to one electronic document of the given electronic document, and total importance of the second electronic document; and (e) calculate the total importance of each of the plurality of electronic documents, by applying (a) to (d) to each of a plurality of pairs of the plurality of electronic documents.