This paper presents an exhaustive study on the
different topologies of ambiguous soft keyboards,
analyzing the text entry average time per
character and the average number of user inputs
necessary for its creation. Various topologies and
design criteria are investigated. In addition, an
analytical model is also proposed. This model
allows one to compare among different topologies
and estimate the sensitivity that different
keyboards offer when compared with dictionary
hit rates. It has been found that ambiguous
keyboards, with six keys, are better to us
