The online and offline worlds are converging. Location-based services, ubiquitous mobile devices and on-the-go social network accessibility are blurring the distinction between in-person activities and their virtual counterpart. An important effect of this convergence is the rapid and powerful impact of offline events (meetings, conferences) on the evolution and temporal dynamics of the online connectivity between members of social and professional networks. However, these effects have been largely unexplored.

Identifying similar professionals is an important task for many core services in professional social networks. Information about users can be obtained from heterogeneous information sources, and different sources provide different insights on user similarity.

Previous work analyzing social networks has mainly focused on binary friendship relations. However, in online social networks the low cost of link formation can lead to networks with heterogeneous relationship strengths (e.g., acquaintances and best friends mixed together). In this case, the binary friendship indicator provides only a coarse representation of relationship information. In this work, we develop an unsupervised model to estimate relationship strength from interaction activity (e.g., communication, tagging) and user similarity. More specifically, we formulate a link-based latent variable model, along with a coordinate ascent optimization procedure for the inference. We evaluate our approach on real-world data from Facebook, showing that the estimated link weights result in higher autocorrelation and lead to improved classification accuracy. 1

Automatic subset selection from a parallel corpus significantly cross-lingual information retrieval (CLIR) performance, in addition to increasing its efficiency. Our selection method extracts relevant training data by incorporating additional criteria (i.e. estimated corpus quality, taxonomy projection and size) in addition to lexical-based criteria. The challenge lies in combining these criteria using a meaningful scoring function that can be used for ranking parallel sentence candidates. We choose weighted geometric mean for its soft-AND properties, and we optimize criteria weights by wrapping the CLIR task in an optimization shell. Due to the indeterminate nature of the search space convexity properties, we have explored continuous reactive tabu search (CRTS), a global optimization method. We use a large parallel corpus in the medical domain to examine the effect of adaptation criteria and their combination on CLIR performance. In our experiments, 100 selected sentences yield 90% of the performance obtained with 5,000 times more in-domain parallel sentences. Our optimized criteria weights considerably outperform the uniform distribution baseline, as well as lexical

This paper examines a new approach to information distillation over temporally ordered documents, and proposes a novel evaluation scheme for such a framework. It combines the strengths of and extends beyond conventional adaptive filtering, novelty detection and non-redundant passage ranking with respect to long-lasting information needs ("tasks" with multiple queries). Our approach supports fine-grained user feedback via highlighting of arbitrary spans of text, and leverages such information for utility optimization in adaptive settings. For our experiments, we defined hypothetical tasks based on news events in the TDT4 corpus, with multiple queries per task. Answer keys (nuggets) were generated for each query and a semi-automatic procedure was used for acquiring rules that allow automatically matching nuggets against system responses. We also propose an extension of the NDCG metric for assessing the utility of ranked passages as a combination of relevance and novelty. Our results show encouraging utility enhancements using the new approach, compared to the baseline systems without incremental learning or the novelty detection components.

An under-explored question in cross-language information retrieval (CLIR) is to what degree the performance of CLIR methods depends on the availability of high-quality translation resources for particular domains. To address this issue, we evaluate several competitive CLIR methods - with different training corpora - on test documents in the medical domain. Our results show severe performance degradation when using a general-purpose training corpus or a commercial machine translation system (SYSTRAN), versus a domain-specific training corpus. A related unexplored question is whether we can improve CLIR performance by systematically analyzing training resources and optimally matching them to target collections. We start exploring this problem by suggesting a simple criterion for automatically matching training resources to target corpora. By using cosine similarity between training and target corpora as resource weights we obtained an average of 5.6% improvement over using all resources with no weights. The same metric yields 99.4% of the performance obtained when an oracle chooses the optimal resource every time.

This paper presents an unsupervised learning approach to building a non-English (Arabic) stemmer. The stemming model is based on statistical machine translation and it uses an English stemmer and a small (10 K sentences) parallel corpus as its sole training resources. No parallel text is needed after the training phase. Monolingual, unannotated text can be used to further improve the stemmer by allowing it to adapt to a desired domain or genre. Examples and results will be given for Arabic, but the approach is applicable to any language that needs affix removal. Our resource-frugal approach results in 87.5% agreement with a state of the art, proprietary Arabic stemmer built using rules, affix lists, and human annotated text, in addition to an unsupervised component. Task-based evaluation using Arabic information retrieval indicates an improvement of 22-38% in average precision over unstemmed text, and 96% of the performance of the proprietary stemmer above.

This paper reports a controlled study on a large number of filter feature selection methods for text classification. Over 100 variants of five major feature selection criteria were examined using four well-known classification algorithms: a Naive Bayesian (NB) approach, a Rocchio-style classifier, a k-nearest neighbor (kNN) method and a Support Vector Machine (SVM) system. Two benchmark collections were chosen as the testbeds: Reuters-21578 and small portion of Reuters Corpus Version 1 (RCV1), making the new results comparable to published results. We found that feature selection methods based on chi2 statistics consistently outperformed those based on other criteria (including information gain) for all four classifiers and both data collections, and that a further increase in performance was obtained by combining uncorrelated and high-performing feature selection methods.The results we obtained using only 3% of the available features are among the best reported, including results obtained with the full feature set.

Techniques for automatically training modules of a natural language generator have recently been proposed, but a fundamental concern is whether the quality of utterances produced with trainable components can compete with hand-crafted template-based or rule-based approaches. In this paper We experimentally evaluate a trainable sentence planner for a spoken dialogue system by eliciting subjective human judgments. In order to perform an exhaustive comparison, we also evaluate a hand-crafted template-based generation component, two rule-based sentence planners, and two baseline sentence planners. We show that the trainable sentence planner performs better than the rule-based systems and the baselines, and as well as the hand-crafted system.

The dialog manager of a spoken dialog system often performs domain dependent functions as well as general dialog tasks. It is possible to separate the domain specific knowledge from knowledge about language using techniques from natural language generation. However a natural language generator often has to be tuned for particular applications. In this work, we describe a new method for automatically training the natural language generator and examine the role that domain specific and domain independent features have on performance. We show that although the general features have the largest impact, the use of domain specific features improves performance, while still retaining the benefits of automatic domain customization through training. 1.