Keen ASR recognizer finds the most likely sequence of words in the spoken audio taking into consideration both the acoustic match (closeness of features extracted from the audio to the acoustic model), as well as the language model.
Decoding graph combines language model with all the other resources (acoustic models, lexicon) in a way that simplifies the decoding process.
KeenASR framework supports programmatic creation of decoding graphs, either from a set of phrases/words users are likely to say, or from an ARPA language model file that you built in yor development sandbox or obtained elsewhere. In either case, if the number of words (ngrams, more precisely) is large, creation of decoding graph on a mobile device may exhaust the memory or take too long, especially on devices with slower CPUs and < 1GB of RAM. In such cases we recommend you create decoding graph in your development sandbox and then bundle it with your app. Contact us if you are interested in large vocabulary dictation and need help with creating decoding graphs for large language models.
ASR Bundle contains acoustic model, lexicon, and various configuration files. ASR Bundles are language specific as well as recognizer type specific. They are typically trained using hundreds or thousands of hours of transcribed spoken audio.