Patent Application
20120029904
The present invention relates generally to language processing, and relates more particularly to translation and dialogue systems.
Interactive translation and dialogue systems are computer systems that converse with human users or enable conversations between human users. Such systems may be monolingual in that a “conversation” occurs between the system and a human user (e.g., a telephone-based dialogue system that provides airline flight information responsive to user commands). Such systems may also be bilingual in that the “conversation” occurs between two human users who speak different languages (in this case, the dialogue system also performs translation between languages). Although the accuracy of interactive translation and dialogue systems is improving, they may still suffer from errors and inaccuracies.
For example, both monolingual and bilingual systems may have trouble understanding a user input. One common instance of this is when a user wants to use a word that is currently unknown to the system. The word may be synonymous with a word already known to the system (e.g., the user uses the term “Madras” for a location that the system knows as “Chennai”) or may be completely unknown to the system.
The present invention relates to a method and apparatus for adding new vocabulary to interactive translation and dialogue systems. In one embodiment, a method for adding a new word to a vocabulary of an interactive dialogue includes receiving an input signal that includes at least one word not currently in the vocabulary, inserting the word into a dynamic component of a search graph associated with the vocabulary, and compiling the dynamic component independently of a permanent component of the search graph to produce a new sub-grammar, where the permanent component comprises a plurality of words that are permanently part of the search graph.
The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.
The present invention relates to a method and apparatus for adding new vocabulary to interactive translation and dialogue systems. Some embodiments of the invention allow new words to be added to an existing system vocabulary by efficiently modifying the system's language models, translation models, pronunciation dictionary, and a corresponding recognizer's search graph.
The system 100 comprises an input device 102 that receives a signal input to the system 100. The input device may be a microphone, transducer, or other device in the case of an audio signal, or may be a keyboard, stylus, writing tablet, scanner, or other device in the case of a textual signal. The input device 102 is optionally coupled to an analog-to-digital converter 104 that processes the input signal to produce a digitized signal.
The optional analog-to-digital converter 104 is in turn coupled to an optional preprocessor 106 that preprocesses the digitized signal to facilitate subsequent recognition processing. In one embodiment, where the input signal is an audio signal, the optional preprocessor 106 is configured to perform at least one of the following on the digitized signal: noise reduction (e.g., reduce background noise), endpointing (i.e., identify start and/or endpoints of the digitized signal), channel normalization (e.g., reduce the effects of different channels and microphones), vocal tract length normalization (e.g., reduce the variability of acoustic features due to different vocal tract lengths), or other kinds of preprocessing.
The preprocessor 106 is coupled to a recognition processor 108. The recognition processor 108 is configured to recognize words and phrases (or portions of words and phrases) in the digitized signal. In one embodiment, where the input signal is an audio signal, the recognition processor 108 is a speech recognition processor, such as an automatic speech recognition (ASR) processor. Given an audio signal containing speech, ASR techniques produce recognition results comprising a textual sequence of words comprising, but not necessarily limited to, a potentially imperfect transcription of the audio signal.
The recognition processor 108 outputs the recognition results to an output generator 110. The output generator 110 generates raw output responsive to the recognition results. For example, in the case of a monolingual dialogue system, the output generator 110 may generate raw data responsive to a user's question (e.g., the arrival time of a given airline flight). In the case of a bilingual dialogue system, the output generator 110 may comprise a translator that translates the recognition results from a first language (i.e., the language of the input signal) into translation results in a second language. The output generator 110 is coupled to one or more translation models 112 and/or optional language models 118 that assist in performing the translation. The translation models 112 and language models 118 form a vocabulary for the system 100, which optionally includes other data sources (grammars, etc).
The output generator 110 then outputs the raw output to an optional synthesizer 114 that generates an output signal representing the content of the raw output. For example, in the monolingual dialogue system discussed above, the output generator 110 may output raw data regarding flight arrival time that is synthesized into the format of a response to the user (e.g., “Flight No. 28 is scheduled to land at 3:00 PM”). In the bilingual dialogue system discussed above, the output generator 110 may output translation results that are synthesized into an output signal representing the content of the input signal in the second language. In one embodiment, where the output signal is an audio signal, the optional synthesizer 114 is a speech synthesizer that synthesizes the translation results into an audio signal that represents the content of the input speech signal in the second language. In another embodiment, where the output signal is a textual signal, the translation may not need to be synthesized and can be output directly from the output generator 110. Alternatively, the optional synthesizer 114 may format the output signal. For example, the synthesizer may format raw data into a natural language response. In one embodiment, the output generator 110 and the optional synthesizer 114 are combined in a single component.
The synthesized translation is then fed to an output device 116. In one embodiment, where the output signal is an audio signal, the output device 116 is a speaker. In another embodiment, where the output signal is a textual signal, the output device 116 is a display.
In one embodiment of the present invention, the recognition processor 108 is further coupled to a vocabulary updater 120. In a further embodiment, the output generator is also coupled to the vocabulary updater 120.
The vocabulary updater 120 operates under the direction of a user to update the system's vocabulary, including the language models 118, translation models 112, and a pronunciation dictionary 122. For example, the vocabulary updater 120 may add new words to one or more language models 118 that are used by the recognition processor 108 and the output generator 110. To this end, the user may use the recognition processor 108 and/or output generator 110 to verify that updates to the vocabulary are effective. The vocabulary updater 120 may also add translations for the new words to the translation models 112 and/or pronunciations for the new words to the pronunciation dictionary 122. The language models 118 may comprise multiple sets of language models for different languages (e.g., a first set of English language models, a second set of Spanish language models, etc.). One embodiment of a method for updating the system's vocabulary is discussed in greater detail with respect to
The new words are provided to the language models 118, translation models 112, and/or pronunciation dictionary 122, which in turn may be accessed by the recognition processor 108 when performing recognition processing or by the optional synthesizer 114 when formatting the output signal, as discussed above.
The system 100 also includes a grammar compiler 124, which generates updated sub-grammars for use by the recognition processor 108. To this end, the grammar compiler 124 receives inputs from the vocabulary updater 120 and the pronunciation dictionary 122.
As discussed above, the system 100 may be configured as a stand-alone device, or may be integrated as part of a larger speech-based system. In addition, the system 100 may be configured as a distributed system wherein one or more of the components discussed above comprises or is integrated as part of a separate device. For example, the recognition processor 108 may remotely access the language models 118 over a network. This allows for easy upgrade of the language models 118 and reduces the processing and memory requirements for the system 100. Alternatively, the input device 102 and/or the output device 116 may be remotely coupled to the system 100. This allows individuals in different locations to converse with each other remotely in different languages.
Although the present invention is described within the context of speech and text processing, those skilled in the art will appreciate that the concepts of the present invention can be easily extended to other types of inputs and outputs as well. For example, the input and/or output can be in video form. This may be helpful, for example, where at least one of the conversants speaks in a sign language.
The method 200 is initialized at step 202 and proceeds to step 204, where the method 200 receives at least one new word for inclusion in the vocabulary. The new word is a word that is not currently in the vocabulary. In some embodiments, the new word is to be added to a language model and a translation model. The new word may be a single word or a sentence or phrase comprising a plurality of words. In one embodiment, the new word is received from a user in connection with a command from the user to add the new word to the vocabulary. In one embodiment, the new word is received in text form (e.g., typed by the user) or in audio form (e.g., spoken by the user).
In step 206, the method 200 inserts the new word into a “placeholder” in a search graph associated with the vocabulary. The search graph comprises two main components: a permanent component that comprises a plurality of words that are permanently part of the search graph and a dynamic component that allows new words to be added (at least temporarily) to the search graph. The dynamic component of the search graph comprises at least one placeholder class inserted into the permanent component to facilitate addition of new words. Thus, a placeholder represents a class of words that is not instantiated (loaded) with the permanent component of the search graph.
In step 208, the method 200 associates one or more translations with the new word and updates the translation models accordingly. In one embodiment, at least one translation is provided by the user. In another embodiment, at least one translation is retrieved from a dictionary or another source.
In step 210, the method 200 associates a pronunciation with the new word to facilitate recognition when the new word occurs in an audio signal. In one embodiment, the pronunciation is provided by the user. In another embodiment, the pronunciation is retrieved from a dictionary (e.g., pronunciation dictionary 122). In another embodiment, the method 200 generates a plurality of potential pronunciations based on the spelling of the new word (e.g., using a letter-to-sound model such as that used by text-to-speech programs, or an automatic pronunciation generator), and then selects the potential pronunciation that best matches (e.g., based on a likelihood score) the new word as pronounced by the user (e.g., using ASR or a similar technique). In one embodiment, step 210 can occur before step 208, or can occur in parallel with step 208.
The pronunciations of the new words generated in accordance with step 210 can also be used in the text-to-speech component of a speech-to-speech translation system. A speech-to-speech translation system uses text-to-speech engines to convert translations into speech. A text-to-speech engine typically analyzes the spelling of a word and generates internal pronunciations based on some model. However, model-based pronunciation generation may have ambiguities and may not always be correct.
In step 211, the method 200 updates the language models in accordance with the new word. In step 212, the method 200 compiles (optimizes and flattens) the placeholder class only, independent of the permanent component of the search graph. Compilation results in a new sub-grammar comprising the words contained in the placeholder class.
The method 200 outputs the new sub-grammar to a recognition processor (such as the recognition processor 108 of
The method 200 thereby adds new vocabulary to the search graph by dynamically updating subgrammars with a newly generated subgrammar comprising new words. Thus, there is no need to reload the permanent component of the search graph, which is fully flattened and optimized at the Hidden Markov Model (HMM) level before the dynamic component is instantiated and expanded. This allows the language models used by the recognition processor to be updated very quickly, as the size of the dynamic component is very small compared to the size of the permanent component. The present invention therefore combines the almost-real-time speed advantage of the fully optimized main grammar with the benefit of the short update time for the compilation of the dynamic component. Moreover, even if the dynamic component is large (i.e., contains many new words), pruning it on the fly during loading allows the update to proceed relatively quickly.
In one embodiment, the dynamic component is loaded for use in rescoring of ASR output. In a further instance of this embodiment, as described above, the dynamic component is used to enhance the accuracy of a language translation system. In this case, the new words may be instantiated as a multi-lingual “translation table” or “phrase table” that is used to supplement a main dictionary, translation table, or translation model used by the language translation system. Once the phrase table is updated, the new words or phrases contained therein may be used in different contexts.
Alternatively, embodiments of the present invention (e.g., language processing 305) can be represented by one or more software applications (or even a combination of software and hardware, e.g., using Application Specific Integrated Circuits (ASIC)), where the software is loaded from a storage medium (e.g., I/O devices 306) and operated by the processor 302 in the memory 304 of the general purpose computing device 300. Thus, in one embodiment, the language processing module 305 for conducting an interactive dialogue described herein with reference to the preceding Figures can be stored on a non-transitory computer readable medium (e.g., RAM, magnetic or optical drive or diskette, and the like).
It should be noted that although not explicitly specified, one or more steps of the methods described herein may include a storing, displaying and/or outputting step as required for a particular application. In other words, any data, records, fields, and/or intermediate results discussed in the methods can be stored, displayed, and/or outputted to another device as required for a particular application. Furthermore, steps or blocks in the accompanying Figures that recite a determining operation or involve a decision, do not necessarily require that both branches of the determining operation be practiced. In other words, one of the branches of the determining operation can be deemed as an optional step.
Although various embodiments which incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.
This application was made with Government support under contract no. NBCHD040058 awarded by the Department of Interior. The Government has certain rights in this invention.
