11. A computer-implemented information searching device, comprising: a non-content characteristics extractor configured to extract one or more non-content characteristics of a document from a document set; an analyzer configured to analyze the extracted non-content characteristics and generate an optimizing tool based on analyzing results; and an optimizer configured to optimize a preliminary search result with the generated optimizing tool, wherein the optimizer comprises: a reliable result selector configured to select, from the preliminary search result, a resulting document sequence having relatively high reliability; a distance calculator configured to calculate a distance from each of the documents to each document of the selected resulting document sequence; an adjusting unit configured to adjust the reliability values of the documents; and an ordering unit configured to arrange the documents in descending order of the adjusted reliability values to obtain optimized results, and wherein the distance from each of the documents in the preliminary search results to the document of the resulting document sequence equals a sum of weights of sides passed through by a directional path between two documents, the distance is infinite when there is no path between the document in the preliminary search results and the document in the resulting document sequence, the distance from one document to itself is zero, the distance L between the document in the preliminary search results and the document in the resulting document sequence is expressed by the following equation when there are plural paths between the two documents, L=1/((1/L 1 )+(1/L 2 )+ . . . +(1/LX)) where, L represents the distance between the two documents, L 1 represents the distance of a path 1 , L 1 represents the distance of a path 2 , and LX represents the distance of a path X.
11. A computer-implemented information searching device, comprising: a non-content characteristics extractor configured to extract one or more non-content characteristics of a document from a document set; an analyzer configured to analyze the extracted non-content characteristics and generate an optimizing tool based on analyzing results; and an optimizer configured to optimize a preliminary search result with the generated optimizing tool, wherein the optimizer comprises: a reliable result selector configured to select, from the preliminary search result, a resulting document sequence having relatively high reliability; a distance calculator configured to calculate a distance from each of the documents to each document of the selected resulting document sequence; an adjusting unit configured to adjust the reliability values of the documents; and an ordering unit configured to arrange the documents in descending order of the adjusted reliability values to obtain optimized results, and wherein the distance from each of the documents in the preliminary search results to the document of the resulting document sequence equals a sum of weights of sides passed through by a directional path between two documents, the distance is infinite when there is no path between the document in the preliminary search results and the document in the resulting document sequence, the distance from one document to itself is zero, the distance L between the document in the preliminary search results and the document in the resulting document sequence is expressed by the following equation when there are plural paths between the two documents, L=1/((1/L 1 )+(1/L 2 )+ . . . +(1/LX)) where, L represents the distance between the two documents, L 1 represents the distance of a path 1 , L 1 represents the distance of a path 2 , and LX represents the distance of a path X. 13. The information searching device as claimed in claim 11 , wherein the preliminary search result includes a result obtained by searching a predetermined data group with a search engine, or a result obtained by another optimizing tool, the result obtained by searching the predetermined data group or by the other optimizing tool is a document sequence, and each document in the document sequence has a reliability value indicating a probability of the document being a target document.