The present invention provides a method and system of measuring knowledge point relationship strength, the method comprising calculating explicit relationship strength for all knowledge points and generating a knowledge point relationship strength matrix M; constructing a weighted and directed graph G according to the knowledge point relationship strength matrix of all knowledge points; calculating knowledge point implicit relationship strength values according to the weighted and directed graph and generating a knowledge point implicit relationship strength matrix I; traversing the knowledge point implicit relationship strength matrix I and updating the knowledge point relationship strength matrix M. The above technical solution may effectively avoid the problem of lack of an absolute measurable value for the determination of relationship strength, incorrect measurement of relationship strength, or unable to discover some stronger relationship strength in the prior art.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A method for measuring knowledge point relationship strength, characterized in comprising the following steps: calculating explicit relationship strength values for all knowledge points and generating a knowledge point relationship strength matrix M; constructing a weighted and directed graph G according to the knowledge point relationship strength matrix of all knowledge points; calculating knowledge point implicit relationship strength values according to the weighted and directed graph and generating a knowledge point implicit relationship strength matrix I; traversing the knowledge point implicit relationship strength matrix I and updating the knowledge point relationship strength matrix M. 2. The method for measuring knowledge point relationship strength according to claim 1, characterized in that the process of calculating explicit relationship strength values for all knowledge points and generating a knowledge point relationship strength matrix M comprises the following steps: calculating knowledge point forward explicit relationship strength values; calculating knowledge point backward explicit relationship strength values; calculating knowledge point explicit relationship strength values according to the knowledge point forward explicit relationship strength values and the knowledge point backward explicit relationship strength values; according to the knowledge point explicit relationship strength values, generating a knowledge point relationship strength matrix M. 3. The method for measuring knowledge point relationship strength according to claim 2, characterized in that the calculation method of knowledge point forward explicit relationship strength values is: f P  ( i , j ) = 2 1 + exp  ( - βμ ) - 1 Wherein, fp (i, j) is the forward explicit relationship strength value from knowledge point oi to knowledge point oj, μ is the number of times knowledge point oj appears in related text of knowledge point oi, β is a control factor, 0.5≦β≦2, i, j are non-negative integers, i, j=1, 2, . . . , n, n is the number of knowledge points; or the calculation method of knowledge point backward explicit relationship strength values is: f N  ( i , j ) = f P  ( j , i ) α Wherein, fN(i, j) is the backward explicit relationship strength value from knowledge point oi to knowledge point oj, α is an association factor, 1≦α≦5, α is a positive integer; fp(j, i) is the forward explicit relationship strength value from knowledge point oj to knowledge point oi. 4. The method for measuring knowledge point relationship strength according to claim 3, characterized in that the calculation method of knowledge point explicit relationship strength values is: f E  ( i , j ) = α  ( f P  ( i , j ) + f N  ( i , j ) ) 1 + α Wherein, fE(i, j) is the explicit relationship strength value from knowledge point oi to knowledge point oj, fp(i, j) is forward explicit relationship strength from knowledge point oi to knowledge point oj, fN(i, j) is the backward explicit relationship strength value from knowledge point oi to knowledge point oj, α is an association factor, 1≦α≦5, and α is a positive integer. 5. The method for measuring knowledge point relationship strength according to claim 1, characterized in that the weighted and directed graph G comprises edges, weights and vertices, wherein, the method of setting edges and weights comprises: if Mij>0, setting a weight of an edge from knowledge point oi to knowledge point oj in the weighted and directed graph G to −ln(Mij); if Mij=0, there is an edge from knowledge point oi to knowledge point oj in the weighted and directed graph G, wherein Mij represents the explicit relationship strength value from knowledge point oi to knowledge point oj; the vertices of the weighted and directed graph G are the same as the vertices in M. 6. The method for measuring knowledge point relationship strength according to claim 1, characterized in that the weighted and directed graph G is represented as a matrix. 7. The method for measuring knowledge point relationship strength according to claim 1, characterized in that, the calculation method of knowledge point implicit relationship strength values is: fI(i, j)=exp(−Cij) Wherein, fI(i, j) is the implicit relationship strength value from knowledge point oi to knowledge point oj, Cij represents the shortest simple path length from knowledge point oi to knowledge point oj in the weighted and directed graph G; if there is not a simple path from knowledge point oi to knowledge point oj, fI(i, j)=0; the value of implicit relationship strength from a knowledge point to itself is set to 0; values of implicit relationship strength fI(i, j) are stored in a matrix to generate a knowledge point implicit relationship strength matrix I. 8. The method for measuring knowledge point relationship strength according to claim 1, characterized in that the process of traversing the knowledge point implicit relationship strength matrix I and updating the knowledge point relationship strength matrix M comprises the following steps: traversing each element of the implicit relationship strength matrix I; determining whether Iij is larger than Mij; if Iij>Mij, reassigning Mij as Mij=Iij and proceeding to the next element of the implicit relationship strength matrix I after updating the knowledge point relationship strength matrix M; if Iij<Mij, proceeding to the next element of the implicit relationship strength matrix I directly, until all elements of the implicit relationship strength matrix I are traversed. 9. The method for measuring knowledge point relationship strength according to claim 7, characterized in that the shortest simple path length Cij is calculated using a Dijkstra algorithm, a SPFA algorithm, a Floyd-Warshall algorithm or a Bellman-Ford algorithm. 10. The method for measuring knowledge point relationship strength according to any of claim 3, characterized in that the control factor β=1 or the association factor α=2. 11. A system for measuring knowledge point relationship strength, characterized in comprising: a knowledge point relationship strength matrix generation module for calculating explicit relationship strength values for all knowledge points and generating a knowledge point relationship strength matrix M; a weighted and directed graph construction module for constructing a weighted and directed graph G according to the knowledge point relationship strength matrix of all knowledge points; a knowledge point implicit relationship strength matrix generation module for calculating knowledge point implicit relationship strength values according to the weighted and directed graph and generating a knowledge point implicit relationship strength matrix I; an update module for traversing the knowledge point implicit relationship strength matrix I and updating the knowledge point relationship strength matrix M. 12. The system for measuring knowledge point relationship strength according to claim 11, characterized in that the knowledge point relationship strength generation module comprises: a forward explicit relationship strength calculation unit for calculating knowledge point forward explicit relationship strength values; a backward explicit relationship strength calculation unit for calculating knowledge point backward explicit relationship strength values; an explicit relationship strength calculation unit for calculating knowledge point explicit relationship strength values according to the knowledge point forward explicit relationship strength values and the knowledge point backward explicit relationship strength values; a knowledge point relationship strength matrix generation unit for, according to the knowledge point explicit relationship strength values, generating a knowledge point relationship strength matrix M. 13. The system for measuring knowledge point relationship strength according to claim 12, characterized in that, the forward explicit relationship strength calculation unit calculates knowledge point forward explicit relationship strength values according to the following equation: f P  ( i , j ) = 2 1 + exp  ( - βμ ) - 1 Wherein, fp(i, j) is the forward explicit relationship strength value from knowledge point oi to knowledge point ok, μ is the number of times knowledge point oj appears in related text of knowledge point oi, β is a control factor, 0.5≦β≦2, i, j are non-negative integers, i, j=1, 2, . . . , n, n is the number of knowledge points; or the backward explicit relationship strength calculation unit calculates knowledge point backward explicit relationship strength values according to the following equation: f N  ( i , j ) = f P  ( j , i ) α Wherein, fN(i, j) is the backward explicit relationship strength value from knowledge point oi to knowledge point oj, α is an association factor, 1≦α≦5, α is a positive integer; fp(j, i) is the forward explicit relationship strength value from knowledge point oj to knowledge point oi. 14. The system for measuring knowledge point relationship strength according to claim 13, characterized in that the knowledge point relationship strength matrix generation module calculates knowledge point explicit relationship strength values according to the following equation: f E  ( i , j ) = α  ( f P  ( i , j ) + f N  ( i , j ) ) 1 + α Wherein, fE(i, j) is the explicit relationship strength value from knowledge point oi to knowledge point oj, fp(i, j) is the forward explicit relationship strength value from knowledge point oi to knowledge point oj, fN(i, j) is the backward explicit relationship strength value from knowledge point oi to knowledge point oj, α is an association factor, 1≦α≦5, and α is a positive integer. 15. The system for measuring knowledge point relationship strength according to claim 11, characterized in that the weighted and directed graph G comprises edges, weights and vertices, wherein, the method of setting edges and weights comprises: if Mij>0, a weight of an edge from knowledge point oi to knowledge point oj in the weighted and directed graph G is set to −ln(Mij); if Mij=0, there is an edge from knowledge point oi to knowledge point oj in the weighted and directed graph G, wherein Mji represents explicit relationship strength from knowledge point oi to knowledge point oj; the vertices of the weighted and directed graph G are the same as the vertices in M. 16. The system for measuring knowledge point relationship strength according to claim 11, characterized in that the weighted and directed graph G is represented as a matrix. 17. The system for measuring knowledge point relationship strength according to claim 12, characterized in that the knowledge point implicit relationship strength matrix generation module calculates knowledge point implicit relationship strength values according to the following equation: fI(i, j)=exp(−Cij) Wherein, fI(i, j) is the implicit relationship strength value from knowledge point oi to knowledge point oj, Cij represents the shortest simple path length from knowledge point oi to knowledge point oj in the weighted and directed graph G; if there is not a simple path from knowledge point oi to knowledge point oj, fI(i, j)=0; the value of implicit relationship strength from a knowledge point to itself is set to 0; values of implicit relationship strength fI(i, j) are stored in a matrix to generate a knowledge point implicit relationship strength matrix I. 18. The system for measuring knowledge point relationship strength according to claim 11, characterized in that the update module comprises: a search unit for traversing each element of the implicit relationship strength matrix I; a determination unit for determining whether Iij is larger than Mij; an update unit for, if Iij>Mij, reassigning Mij as Mij=Iij and proceeding to the next element of the implicit relationship strength matrix I after updating the knowledge point relationship strength matrix M; if Iij<Mij, proceeding to the next element of the implicit relationship strength matrix I directly, until all elements of the implicit relationship strength matrix I are traversed; or the shortest simple path length Cij is calculated using a Diikstra algorithm, a SPFA algorithm, a Floyd-Warshall algorithm or a Bellman-Ford algorithm. 19. (canceled) 20. The system for measuring knowledge point relationship strength according to claim 13, characterized in that the control factor β=1 or the association factor α=2. 21. One or more computer readable mediums having stored thereon computer-executable instructions that when executed by a method of measuring knowledge point relationship strength, the method comprising: calculating explicit relationship strength for all knowledge points and generating a knowledge point relationship strength matrix M; constructing a weighted and directed graph G according to the knowledge point relationship strength matrix of all knowledge points; calculating knowledge point implicit relationship strength values according to the weighted and directed graph and generating a knowledge point implicit relationship strength matrix I; traversing the knowledge point implicit relationship strength matrix I and updating the knowledge point relationship strength matrix M.