1. A computer readable storage medium storing instructions, which, when executed by a computer, perform a method for representing a discourse input, the method comprising: receiving a discourse input; and parsing the discourse input to generate a discourse representation data structure (DRS) that represents entities in the discourse input and linguistic relationships of the entities, the DRS comprising an array of boxes, each box including a set of box elements with associated arguments having markers, wherein the box elements are normalized by deleting unused boxes from the DRS and are initially sorted in a preliminary order based on a box and box element normal form regardless of the markers, and wherein the markers are in a normalized form in the DRS, and the boxes and box elements are sorted based on the preliminary order and based on the marker normal form to obtain the DRS in a normal form, the box elements and associated arguments in the DRS in the normal form including a semantic representation of semantic content of the discourse input.