1. A method of domain knowledge structure generation in online learning materials, the method comprising: crawling, by one or more processors, electronic learning materials stored at least temporarily in one or more non-transitory storage media; extracting, by the one or more processors, structural information from the electronic learning materials; extracting, by the one or more processors, knowledge points from the electronic learning materials based at least partially on an organization of the electronic learning materials as indicated by the extracted structural information; locating, by the one or more processors, positions of each of the knowledge points within each of the learning materials; comparing, by the one or more processors, relative positions of knowledge points in the learning materials in which the knowledge points are present; inferring, by the one or more processors, hierarchy and dependency relationships between the knowledge points based at least partially on the relative positions of the knowledge points; aligning, by the one or more processors, one or more of the knowledge points with at least one specific portion of one or more of the learning materials, wherein each of the specific portions include one of the located positions of the corresponding knowledge point within the learning materials; and generating, by the one or more processors, a domain knowledge structure including the extracted knowledge points organized at least partially according to the inferred hierarchy and dependency relationships and including the aligned learning materials.