1. A method of generating a customized document about a product, the product comprising a plurality of components, the method comprising: a) providing a user with a document manager input interface on a computer, the input interface including a template manager module, a data pools 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 template based on a plurality of predefined data elements arranged in a tree-like data structure using the template manager module, the predefined data elements being retrieved from a parts library contained in the document builder module and defining parts and sections to be listed in the template; c) on the computer, creating the customized document from the defined template using the document builder module; d) on the computer, editing the customized document using the document editor module by using content-specific pull-down menus on the computer to edit one or more of the predefined data elements and thereby generating revised data elements and storing the revised data elements in a relational database storing the customized document; e) on the computer, deconstructing the 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 a business rule and applying the business rule to the textual data elements of the document using the automatic text generator module; f) on the computer, modifying data that is standard in particular data structures and customizing the data for particular applications using a data pools manager module; g) on the computer, establishing effectivity associations, using the effectivity interface module, for a given component of the product, defining the manner in which a change to a given component is propagated throughout the customized document; h) in response to a 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; i) synthesizing text from the revised data elements according to the (i) the structure defined be the template manager module, (ii) the edits made using the document editor module; (iii) the business rule applied by the user using the automatic text generator module, (iv) the customization data provided by the data pools manager module, and (v) the effectivity associations established by the user; and j) generating and publishing the customized document.