We propose an approach for identifying the speech acts of speakers’ utterances in conversational spoken dialogue that involves using semantic dependency graphs with probabilistic context-free grammars (PCFGs). The semantic dependency graph based on the HowNet knowledge base is adopted to model the relationships between words in an utterance parsed by PCFG. Dependency relationships between words within the utterance are extracted by decomposing the semantic dependency graph according to predefined events. The corresponding values of semantic slots are subsequently extracted from the speaker's utterances according to the corresponding identified speech act. The experimental results obtained when using the proposed approach indicated that the accuracy rates of speech act detection and task completion were 95.6% and 77.4% for human-generated transcription (REF) and speech-to-text recognition output (STT), respectively, and the average numbers of turns of each dialogue were 8.3 and 11.8 for REF and STT, respectively. Compared with Bayes classifier, partial pattern tree, and Bayesian-network-based approaches, we obtained 14.1%, 9.2%, and 3% improvements in the accuracy of speech act identification, respectively.

An approach is proposed for Chinese spelling error detection and correction, in which an inverted index list with a rescoring mechanism is used. The inverted index list is a structure for mapping from word to desired sentence, and for representing nodes in lattices constructed through character expansion (according to predefined phonologically and visually similar character sets). Pruning based on a contextual dependency confidence measure was used to markedly reduce the search space and computational complexity. Relevant mapping relations between the original input and desired input were obtained using a scoring mechanism composed of class-based language and maximum entropy correction models containing character, word, and contextual features. The proposed method was evaluated using data sets provided by SigHan 7 bakeoff. The experimental results show that the proposed method achieved acceptable performance in terms of recall rate or precision rate in error sentence detection and error location detection, and it outperformed other approaches in error location detection and correction.

This article presents a probabilistic scheme for detecting the interruption point (IP) in spontaneous speech based on inter-syllable boundary-based prosodic features. Because of the high error rate in spontaneous speech recognition, a combined acoustic model considering both syllable and subsyllable recognition units, is firstly used to determine the inter-syllable boundaries and output the recognition confidence of the input speech. Based on the finding that IPs always occur at inter-syllable boundaries, a probability distribution of the prosodic features at the current potential IP is estimated. The Conditional Random Field (CRF) model, which employs the clustered prosodic features of the current potential IP and its preceding and succeeding inter-syllable boundaries, is employed to output the IP likelihood measure. Finally, the confidence of the recognized speech, the probability distribution of the prosodic features and the CRF-based IP likelihood measure are integrated to determine the optimal IP sequence of the input spontaneous speech. In addition, pitch reset and lengthening are also applied to improve the IP detection performance. The Mandarin Conversional Dialogue Corpus is adopted for evaluation. Experimental results show that the proposed IP detection approach obtains 10.56% and 6.5% more effective results than the hidden Markov model and the Maximum Entropy model respectively under the same experimental conditions. Besides, the IP detection error rate can be further reduced by 9.15% using pitch reset and lengthening information. The experimental results confirm that the proposed model based on inter-syllable boundary-based prosodic features can effectively detect the interruption point in spontaneous Mandarin speech.

This paper presents an approach to speaker clustering using decision tree-based phone cluster models (DT-PCMs). In this approach, phone clustering is first applied to construct the universal phone cluster models to accommodate acoustic characteristics from different speakers. Since pitch feature is highly speaker-related and beneficial for speaker identification, the decision trees based on multi-space probability distributions (MSDs), useful to model both pitch and cepstral features for voiced and unvoiced speech simultaneously, are constructed. In speaker clustering based on DT-PCMs, contextual, phonetic, and prosodic features of each input speech segment is used to select the speaker-related MSDs from the MSD decision trees to construct the initial phone cluster models. The maximum-likelihood linear regression (MLLR) method is then employed to adapt the initial models to the speaker-adapted phone cluster models according to the input speech segment. Finally, the agglomerative clustering algorithm is applied on all speaker-adapted phone cluster models, each representing one input speech segment, for speaker clustering. In addition, an efficient estimation method for phone model merging is proposed for model parameter combination. Experimental results show that the MSD-based DT-PCMs outperform the conventional GMM- and HMM-based approaches for speaker clustering on the RT09 tasks.

This paper presents an approach to interruption point (IP) detection of spontaneous speech based on conditional random fields using prior knowledge and multiple features. The features adopted in this study consist of subsyllable boundaries and prosodic features. Conditional random fields (CRFs) and variable-length contextual features are employed for IP modeling. In order to apply the features with continuous values to the CRF models, the K-means clustering algorithm is adopted for the quantization of the prosodic features. In the experimental results, Mandarin Conversional Dialogue Corpus (MCDC) was used to evaluate the proposed method. The IP detection error rate achieved almost 20% reduction in Rt04 measure. The experimental results show that the proposed model can effectively detect the interruption point in spontaneous speech.

Abstract This article presents a bilingual ontology‐based dialog system with multiple services. An ontology‐alignment algorithm is proposed to integrate ontologies of different languages for cross‐language applications. A domain‐specific ontology is further extracted from the bilingual ontology using an island‐driven algorithm and a domain corpus. This study extracts the semantic words/concepts using latent semantic analysis (LSA). Based on the extracted semantic words and the domain ontology, a partial pattern tree is constructed to model the speech act of a spoken utterance. The partial pattern tree is used to deal with the ill‐formed sentence problem in a spoken‐dialog system. Concept expansion based on domain ontology is also adopted to improve system performance. For performance evaluation, a medical dialog system with multiple services, including registration information, clinic information, and FAQ information, is implemented. Four performance measures were used separately for evaluation. The speech act identification rate was 86.2%. A task success rate of 77% was obtained. The contextual appropriateness of the system response was 78.5%. Finally, the rate for correct FAQ retrieval was 82%, an improvement of 15% over the keyword‐based vector‐space model. The results show the proposed ontology‐based speech‐act identification is effective for dialog management.

Negative and stressful life events play a significant role in triggering depressive episodes. Psychiatric services that can identify such events efficiently are vital for mental health care and prevention. Meaningful patterns, e.g.,, must be extracted from psychiatric texts before these services can be provided. This study presents an evolutionary text-mining framework capable of inducing variable-length patterns from unannotated psychiatry Web resources. The proposed framework can be divided into two parts: 1) a cognitive motivated model such as hyperspace analog to language (HAL) and 2) an evolutionary inference algorithm (EIA). The HAL model constructs a high-dimensional context space to represent words as well as combinations of words. Based on the HAL model, the EIA bootstraps with a small set of seed patterns, and then iteratively induces additional relevant patterns. To avoid moving in the wrong direction, the EIA further incorporates relevance feedback to guide the induction process. Experimental results indicate that combining the HAL model and relevance feedback enables the EIA to not only induce patterns from the unannotated Web corpora, but also achieve useful results in a reasonable amount of time. The proposed framework thus significantly reduces reliance on annotated corpora.

Psychiatric query document retrieval can assist individuals to locate query documents relevant to their depression-related problems efficiently and effectively. By referring to relevant documents, individuals can understand how to alleviate their depression-related symptoms according to recommendations from health professionals. This work presents an extended probabilistic Hyperspace Analog to Language ( epHAL ) model to achieve this aim. The epHAL incorporates the close temporal associations between words in query documents to represent word cooccurrence relationships in a high-dimensional context space. The information flow mechanism further combines the query words in the epHAL space to infer related words for effective information retrieval. The language model perplexity is considered as the criterion for model optimization. Finally, the epHAL is adopted for psychiatric query document retrieval, and indicates its superiority in information retrieval over traditional approaches.

This investigation presents a novel approach to detecting and correcting the edit disfluency in spontaneous speech. Hypothesis testing using acoustic features is first adopted to detect potential interruption points (IPs) in the input speech. The word order of the cleanup utterance is then cleaned up based on the potential IPs using a class-based cleanup language model, the deletable region and the correction are aligned using an alignment model. Finally, log linear weighting is applied to optimize the performance. Using the acoustic features, the IP detection rate is significantly improved especially in recall rate. Based on the positions of the potential IPs, the cleanup language model and the alignment model are able to detect and correct the edit disfluency efficiently. Experimental results demonstrate that the proposed approach has achieved error rates of 0.33 and 0.21 for IP detection and edit word deletion, respectively.

This investigation presents a novel approach to semantic segment extraction and matching for retrieving information from Internet FAQs with natural language queries. Two semantic segments, the question category segment (QS) and the keyword segment (KS), are extracted from the input queries and the FAQ questions with a semiautomatically derived question-semantic grammar. A semantic matching method is presented to estimate the similarity between the semantic segments of the query and the questions in the FAQ collection. Additionally, the vector space model (VSM) is adopted to measure the similarity between the query and the answers of the QA pairs. Finally, a multistage ranking strategy is adopted to determine the optimally performing combination of similarity metrics. The experimental results illustrate that the proposed method achieves an average rank of 4.52 and a top-10 recall rate of 90.89 percent. Compared with the query-expansion method, this method improves the performance by 4.82 places in the average rank of correct answers, 25.34 percent in the top-5 recall rate, and 5.21 percent in the top-10 recall rate.

This investigation presents an approach to domain-specific FAQ (frequently-asked question) retrieval using independent aspects. The data analysis classifies the questions in the collected QA (question-answer) pairs into ten question types in accordance with question stems. The answers in the QA pairs are then paragraphed and clustered using latent semantic analysis and the K-means algorithm. For semantic representation of the aspects, a domain-specific ontology is constructed based on WordNet and HowNet. A probabilistic mixture model is then used to interpret the query and QA pairs based on independent aspects; hence the retrieval process can be viewed as the maximum likelihood estimation problem. The expectation-maximization (EM) algorithm is employed to estimate the optimal mixing weights in the probabilistic mixture model. Experimental results indicate that the proposed approach outperformed the FAQ-Finder system in medical FAQ retrieval.

This paper presents an ontology-based partial pattern tree to identify the speech act in a spoken dialogue system. This study first extracts the key words/concepts in an application domain using latent semantic analysis (LSA). A partial pattern tree is used to deal with the ill-formed sentence problem in a spoken dialogue system. Concept expansion based on domain ontology is adopted to improve system performance. For performance evaluation, a medical dialogue system with multiple services, including registration information, clinic information and FAQ information, is implemented. Four performance measures were separately used for evaluation. The speech act identification rate achieves 86.2%. A Task Success Rate of 77% is obtained. The contextual appropriateness of the system response is 78.5%. Finally, the correct rate for FAQ retrieval is 82% with an improvement of 15% in comparison with the keyword-based vector space model. The results show the proposed ontology-based partial pattern tree is effective for dialogue management.