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Information ordering is a nontrivial task in multi-document summarization (MDS), which typically relies on the traditional vector space model (VSM) notorious for semantic deficiency. In this article, we propose a novel event-enriched VSM to alleviate the problem by building event semantics into sentence representations. The mediation of event information between sentence and term, especially in the news domain, has an intuitive appeal as well as technical advantage in common sentence-level operations such as sentence similarity computation. Inspired by the block-style writing by humans, we base the sentence ordering algorithm on sentence clustering. To accommodate the complexity introduced by event information, we adopt a soft-to-hard clustering strategy on the event and sentence levels, using expectation-maximization clustering and K-means, respectively. For the purpose of cluster-based sentence ordering, the event-enriched VSM enables us to design an ordering algorithm to enhance event coherence computed between sentence and sentence-context pairs. Drawing on the findings of earlier research, we also incorporate topic continuity measures and time information into the scheme. We evaluate the performance of the model and its variants automatically and manually, with experimental results showing clear advantage of the event-based model over baseline and non-event-based models in information ordering for multi-document news summarization. We are confident that the event-enriched VSM has even greater potential in summarization and beyond, which awaits further research. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The existence of structural ambiguity in modifying clauses renders noun phrase (NP) extraction from running Chinese texts complicated. It is shown from previous experiments that nearly 33% of the errors in an NP extractor were actually caused by the use of clause modifiers. For example, consider the sequence “V + NP[sub 1]+ (of) + NP[sub 0].” It can be interpreted as two alternatives, a verb phrase (i.e., [V[NP[sub 1]+ + NP[sub 0]][sub NP]][sub VP]) or a noun phrase (i.e., [[V NP[sub 1]][sub VP]+ + NP[sub 0]][sub NP]). To resolve this ambiguity, syntactical, contextual, and semantics-based approaches are investigated in this article. The conclusion is that the problem can be overcome only when the semantic knowledge about words is adopted. Therefore, a structural disambiguation algorithm based on lexical association is proposed. The algorithm uses the semantic class relation between a word pair derived from a standard Chinese thesaurus, , to work out whether a noun phrase or a verb phrase has a stronger lexical association within the collocation. This can, in turn, determine the intended phrase structure. With the proposed algorithm, the best accuracy and coverage are 79% and 100%, respectively. The experiment also shows that the backed-off model is more effective for this purpose. With this disambiguation algorithm, parsing performance can be significantly improved. [ABSTRACT FROM AUTHOR]