The document discusses interaction design and linguistics. It begins with an introduction to descriptive linguistics concepts like surface structure, deep structure, syntax, lexicon, elements, constructs and compositions. These concepts are then applied to design languages, using highway signs as an example. Highway sign language is presented as having well-defined elements, constructs and syntax, along with some allowances for variation between states. The discussion suggests interaction design could benefit from grounding in theoretical foundations like those found in linguistics.