• (A) in broad terms, the kind of technical and software framework within which human system interaction takes place (e.g., wimp, mobile, tangible)
• (B) an idea from the world that is used in the interface to help the user understand what to do (e.g., click on tabs to change window contents, use shopping cart to store items to purchase)
• (C) what the human does to make inputs and receive information from the system (e.g., click and drag an object, talk to an object, move self closer to an object, converse with an entity, etc)
• (D) the conceptual model used to guide the design of the interface.