Patent ID: 8225203

Claim:
A text input apparatus, comprising: a display including a touch sensitive display surface; digital data storage containing a vocabulary database including multiple vocabulary entries; and coupled to the display and the storage, a processor programmed to perform operations comprising: directing the display to show an arrangement of keys, each key representing one or more characters; via the display surface, receiving user input comprising a single continuous trace contacting multiple of the keys in an order, including a start key, an end key, and any intervening keys between the start key and the end key; defining an input sequence including the contacted keys and also including any auxiliary keys comprising keys exhibiting prescribed proximity to the contacted keys; comparing the input sequence to candidate entries from the vocabulary, including the following operations for each candidate entry: computing a set-edit-distance metric to calculate a matching metric between said input sequence and the candidate entry; where: the set-edit-distance computation imposes a penalty for, omitting from the candidate word all keys from a first group comprising the start key and auxiliary keys to the start key; the set-edit-distance computation imposes a penalty for omitting from the candidate word all keys from a second group comprising the end key and auxiliary keys to the end key; the set-edit-distance computation imposes a penalty for omitting from the candidate word all keys from a third group comprising any contacted keys and their auxiliaries where at least a prescribed minimum change in direction of the trace occurs; the set-edit-distance computation does not impose any penalty for omitting from the candidate word any key of the input sequence outside all of the first, second, and third groups; and the set-edit-distance computation does not impose any penalty for using any key in the input sequence twice or more in succession in the candidate word; and ranking the candidate words according to criteria including at least the computed set-edit-distance metric, and providing an output of at least some of the ranked candidate words.