1. A non-transitory computer readable storage medium storing at least one program configured for execution by at least one processor of a computer system, the at least one program comprising instructions to: obtain a domain model comprising a set of entity types having corresponding properties and relationships between entities in a set of entities, wherein the domain model is characterized by a domain grammar; receive a first tag layout of a first source document obtained from a first information source associated with the domain model, the first tag layout comprising: (i) a plurality of user-provided navigational tags, wherein a user-provided navigational tag in the plurality of a user-provided navigational tags indicates a navigational position of the first source document relative to a second source document, from the first information source, navigationally connected with the first source document, and (ii) a plurality of corresponding user-identified tokens in the first source document, wherein a user-identified token in the plurality of corresponding user-identified tokens includes a portion of content of the first source document; select a page grammar in plurality of page grammars for the first source document in accordance with the plurality of user provided navigational tags; extract information from a third source document having a predefined degree of tag layout similarity to the first source document using the page grammar, wherein the second source document is obtained from a second information source; and transform the information extracted from the second source document in accordance with the domain grammar, thereby extracting and integrating information from a plurality of information sources.