Semantic Snapping

Snapping or "gravity fields" is a technique used in conjunction with dragging. As an object is dragged near an interesting point on the screen, it is snapped to that point. This technique is extremely useful in a range of interactions such as situations where objects are connected together or aligned. Semantic snapping is a class of snapping techniques that extend the basic snapping paradigm -- which is based solely on geometry -- to include semantic tests and a high degree of dynamic feedback. These techniques allow semantic feedback to be applied at the level of lexical interactions.

Examples of the use of semantic snapping include the ER-diagram editor shown below. Here as a rubber-banded line is dragged from an entity symbol it snaps to a relationship symbol with simple positive feedback.

However, if the user attempts to connect two entities directly without an intervening relationship symbol, a special "anti-snap" occurs indicating a problem and providing negative feedback.

As an additional example, both positive and negative feedback are shown below in a desktop interface application (created with the Penguims end-user interface specification environment).

Hudson, Scott, E., "Semantic Snapping: A Technique for Semantic Feedback at the Lexical Level", Proceedings of the 1990 SIGCHI Conference, pp. 65-70, April 1990.

Henry, Tyson, R., Hudson, Scott, E., and Newell, Gary, N., "Integrating Snapping and Gesture in a User Interface Toolkit", Proceedings of the ACM Symposium on User Interface Software and Technology, pp. 112-122, October 1990.