1. A method comprising: receiving a request to convert a first hierarchical structure into a first graphical tree representing a requirements model, the first hierarchical structure comprising a plurality of elements and relationships among the plurality of elements; identifying each of the plurality of elements of the first hierarchical structure and the relationships among the plurality of elements; generating the first graphical tree based on each of the plurality of elements and the relationships among the plurality of elements, the first graphical tree comprising a plurality of shapes, each of the plurality of shapes associated with a respective one of the plurality of elements; displaying the first graphical tree representing the requirements model, each of the plurality of shapes including identifying text; displaying a second graphical tree representing a functional model simultaneously with the first graphical tree in response to a first user request, the second graphical tree comprising a plurality of shapes connected by branches; displaying a third graphical tree representing a logical model simultaneously with the first graphical tree and the second graphical tree in response to a second user request, the third graphical tree comprising a plurality of shapes connected by branches, the third graphical tree representing the logical model based on information from the first graphical tree representing the requirements model and the second graphical tree representing the functional model; receiving user input associating one of the plurality of shapes of the first graphical tree associated with a requirements element with one of the plurality of shapes of the second graphical tree associated with a functional element; storing association information in a file associated with the one of the plurality of shapes of the first graphical tree and in a file associated with the one of the plurality of shapes associated with the second graphical tree; and displaying association information for a particular one of the plurality of shapes of the first graphical tree in response to a user request to display association information, the user request to display association information comprising a user moving a graphical cursor over the particular one of the plurality of the shapes of the first graphical tree, the displaying association information comprising: highlighting the particular one of the plurality of shapes of the first graphical tree; highlighting a particular one of the plurality of shapes of the second graphical tree associated with the particular one of the plurality of shapes of the first graphical tree and highlighting a particular one of the plurality of shapes of the third graphical tree associated with the particular one of the plurality of shapes of the first graphical tree.