Ambiguities in sketch-based interfaces

Sketch-based interaction is an intuitive, simple communication method. However, it has several critical aspects, due to difficulties during the interpretation step by the computer side. These mainly derive from the semantic gap between the user's communicative intention and how he/she is able to convey it. The interpretation must also consider the deletion and over-tracing actions. This introduces further ambiguities that make it difficult to interpret the user's communicative intention. To deal with these problems, this paper provides a classification of ambiguities for sketch-based interfaces, based on experimental observations from a group of users. Ambiguities are caused by inaccuracy, approximation of the represented reality, user's indecision and deletion or retracing of parts of the sketch. This paper presents some useful situations to give an overview on ambiguities by considering information strictly related to the user's behaviour, considering spatial and temporal information in the drawing process and the user's intention.