Practical Collapsed Stochastic Variational Inference for the HDP

Recent advances have made it feasible to apply the stochastic variational paradigm to a collapsed representation of latent Dirichlet allocation (LDA). While the stochastic variational paradigm has successfully been applied to an uncollapsed representation of the hierarchical Dirichlet process (HDP), no attempts to apply this type of inference in a collapsed setting of non-parametric topic modeling have been put forward so far. In this paper we explore such a collapsed stochastic variational Bayes inference for the HDP. The proposed online algorithm is easy to implement and accounts for the inference of hyper-parameters. First experiments show a promising improvement in predictive performance.Comment: NIPS Workshop; Topic Models: Computation, Application, and Evaluatio

When Politicians Talk: Assessing Online Conversational Practices of Political Parties on Twitter

Assessing political conversations in social media requires a deeper understanding of the underlying practices and styles that drive these conversations. In this paper, we present a computational approach for assessing online conversational practices of political parties. Following a deductive approach, we devise a number of quantitative measures from a discussion of theoretical constructs in sociological theory. The resulting measures make different - mostly qualitative - aspects of online conversational practices amenable to computation. We evaluate our computational approach by applying it in a case study. In particular, we study online conversational practices of German politicians on Twitter during the German federal election 2013. We find that political parties share some interesting patterns of behavior, but also exhibit some unique and interesting idiosyncrasies. Our work sheds light on (i) how complex cultural phenomena such as online conversational practices are amenable to quantification and (ii) the way social media such as Twitter are utilized by political parties.Comment: 10 pages, 2 figures, 3 tables, Proc. 8th International AAAI Conference on Weblogs and Social Media (ICWSM 2014

SesameTM: Building Topic Maps on RDF

Over the past decade RDF has developed to become the dominant standard for representation and interchange of structured data on the web. In portal development, widely unrecognized by Semantic Web research, subject-centric topic maps are actively used and have evolved from an ancient SGML and intermittent XML-based standard to a pure data model. This data model can be represented as a graph and served various integration strategies, put forward over the past years, as a starting point. However, none of these strategies really appreciates the way in which the technologies are used resulting in a poor tool interoperability. To overcome this state we propose a Topic Maps engine acting as congurable wrapper for Sesame. The software library we develop and describe in this paper implements the Topic Maps Application Programming Interface (TMAPI) enabling the usage of Topic Maps infrastructure instead of working at the level of RDF triples

Characterizing the Global Crowd Workforce: A Cross-Country Comparison of Crowdworker Demographics

Micro-task crowdsourcing is an international phenomenon that has emerged during the past decade. This paper sets out to explore the characteristics of the international crowd workforce and provides a cross-national comparison of the crowd workforce in ten countries. We provide an analysis and comparison of demographic characteristics and shed light on the significance of micro-task income for workers in different countries. This study is the first large-scale country-level analysis of the characteristics of workers on the platform Figure Eight (formerly CrowdFlower), one of the two platforms dominating the micro-task market. We find large differences between the characteristics of the crowd workforces of different countries, both regarding demography and regarding the importance of micro-task income for workers. Furthermore, we find that the composition of the workforce in the ten countries was largely stable across samples taken at different points in time