1. A method of generating a customized document about a product, the method comprising: a) providing a user with a document manager input interface on a computer, the input interface including a definition manager module, an electronic library manager module, an automatic text generator module, a document editor module, an effectivity interface module, and a document builder module; b) on the computer, defining a document definition based on a plurality of predefined data elements arranged in a tree-like data structure using the definition manager module, the predefined data elements being retrieved from a parts library contained in the document builder module, wherein the document definition comprises at least one of (i) organization of sections of the customized document, (ii) maintenance codes specific to the product, and (iii) page formatting information; c) on the computer, creating the customized document from the document definition using the definition manager module; d) on the computer, storing the customized document in a relational database; e) on the computer, editing one or more of the predefined data elements using the document editor module by using content-specific selection menus to generate revised data elements that are stored in the relational database; f) on the computer, deconstructing syntax of textual data elements that are syntactically joined with linguistic rules, specifying a category in which to place a business rule, generating one or more tasks associated with the business rule, and applying the business rule to the textual data elements of the customized document using the automatic text generator module; g) on the computer, modifying given data that is standard in particular data structures, and customizing the given data for particular applications using the electronic library manager module; h) on the computer, establishing effectivity associations, using the effectivity interface module, for a given component of the product, and thereby defining a manner in which a change to the given component is propagated throughout the customized document; i) in response to the user making the change to the given component via the effectivity interface module, propagating the change throughout the customized document according to the effectivity associations established by the user; j) synthesizing text from the revised data elements according to (i) the document definition defined by the document definition module, (ii) edits made by the user via the document editor module, (iii) the business rule applied by the user via the automatic text generator module, (iv) the customized data provided by the electronic library manager module, and (v) the effectivity associations established via the effectivity interface module; and k) generating and publishing the customized document.