We present a new weighted session similarity measure to capture the browsing interests of users in web usage profiles discovered from web log data. We base our similarity measure on the reasonable assumption that when users spend longer times on pages or revisit pages in the same session, then very likely, such pages are of greater interest to the user. The proposed similarity measure combines structural similarity with session-wise page significance. The latter, representing the degree of user interest, is computed using frequency and duration of a page access. Web usage profiles are generated using this similarity measure by applying a fuzzy clustering algorithm to web log data. For evaluating the effectiveness of the proposed measure, we adapt two model-based collaborative filtering algorithms for recommending pages. Experimental results show considerable improvement in overall performance of recommender systems as compared to use of other existing similarity measures.

Thee technical program of this workshop consists of presentations of recent, high-quality research contributions, which were selected by the workshop's international program committee in a peer review process. Five long papers and three short papers were accepted for presentation. The papers address a variety of topics in the context of personalization and recommender systems such as new techniques for group recommendation; user modeling and recommendation on the social web; automated content analysis for personalization and recommendation and mobile advertising.

In crowdsourced relevance judging, each crowd workertypically judges only a small number of examples,yielding a sparse and imbalanced set of judgments inwhich relatively few workers influence output consensuslabels, particularly with simple consensus methodslike majority voting. We show how probabilistic matrixfactorization, a standard approach in collaborative filtering,can be used to infer missing worker judgments suchthat all workers influence output labels. Given completeworker judgments inferred by PMF, we evaluate impactin unsupervised and supervised scenarios. In thesupervised case, we consider both weighted voting andworker selection strategies based on worker accuracy.Experiments on a synthetic data set and a real turk dataset with crowd judgments from the 2010 TREC RelevanceFeedback Track show promise of the PMF approachmerits further investigation and analysis.

We explore the use of an interface to mark pairs of points on two images which are in "correspondence" with one another, as a way of collecting part annotations. The interface allows annotations of visual categories that are structurally diverse, such as chairs and buildings, where it is difficult to define a set of parts, or landmarks, that are consistent, namable or uniquely defined across all instances of the category. It allows flexibility in annotation - the landmarks can be instance specific, are not constrained by language, could be many to one, etc and requires little category specific instructions. We compare our approach to two popular methods of collecting part annotations, (1) drawing bounding boxes for a set of parts, and (2) annotating a set of landmarks, in terms of annotation setup overhead, cost, difficulty, applicability and utility, and identify scenarios where one method is better suited than the others. Preliminary experiments suggest that such annotations between a sparse set of pairs can be used to bootstrap many high level visual recognition tasks such as part discovery and semantic saliency.

With the proliferation of online labor markets and other social computing platforms, online experiments have become a low-cost and scalable way to empirically test hypotheses and mechanisms in both human computation and social science. Yet, despite the potential in designing more powerful and expressive online experiments using multiple subjects, researchers still face many technical and logistical difficulties. We see synchronous and longitudinal experiments involving real-time interaction between participants as a dual-use paradigm for both human computation and social science, and present TurkServer, a platform that facilitates these types of experiments on Amazon Mechanical Turk. Our work has the potential to make more fruitful online experiments accessible to researchers in many different fields.

Contextual knowledge is essential in answering questions given specific observations. While recent approaches to building commonsense knowledge basesvia text mining and/or crowdsourcing are successful,contextual knowledge is largely missing. To addressthis gap, this paper presents SocialExplain, a novel approach to acquiring contextual commonsense knowledge from explanations of social content. The acquisition process is broken into two cognitively simple tasks:to identify contextual clues from the given social content, and to explain the content with the clues. An experiment was conducted to show that multiple piecesof contextual commonsense knowledge can be identi-fied from a small number of tweets. Online users verified that 92.45% of the acquired sentences are good,and 95.92% are new sentences compared with existingcrowd-sourced commonsense knowledge bases.

We report results from a human computation study that tests the extent to which output agreement games are better than traditional methods in terms of increasing quality of labels and motivation of voluntary workers on a task with a gold standard. We built an output agreement game that let workers recruited from Amazon's Mechanical Turks label the semantic textual similarity of 20 sentence pairs. To compare and test the effects of the major components of the game, we created interfaces that had different combinations of a gaming environment (G), social interaction (S), and feedback (F). Our results show that the main reason that an output agreement game can collect more high-quality labels is the gaming environment (scoring system, leaderboard, etc). On the other hand, a worker is much more motivated to voluntarily do the task if he or she can do it with another worker (i.e., with social interaction). Our analysis provides human computation researchers important insight on understanding how and why the method of Game with a Purpose (GWAP) can generate high-quality outcomes and motivate more voluntary workers.

Human computation is a relatively new research area that studies how to build intelligent systems that involve human computers, with each of them performing computation (for example, image classification, translation, and protein folding) that leverages human intelligence, but challenges even the most sophisticated AI algorithms that exist today. With the immense growth of the Web, human computation systems can now leverage the abilities of an unprecedented number of Internet users to perform complex computation. Various genres of human computation applications are available today, including games with a purpose (for example, the ESP Game) that generate useful data through gameplay, crowdsourcing marketplaces (for example, Amazon Mechanical Turk) that coordinate workers to perform tasks for monetary rewards, and identity verification systems (for example, reCAPTCHA) that generate useful data through users performing computation for access to online content. Despite the variety of human computation applications, there exist many common core research issues. How can we design mechanisms for querying human computers in such a way that incentivizes or encourages truthful responses?

This paper outlines a study that investigates spatial language for use in human-robot communication. The scenario studied is a home setting in which the elderly resident has misplaced an object, such as eyeglasses, and the robot will help the resident find the object. We present results from phase I of the study in which we investigate spatial language generated to a human addressee or a robot addressee in a virtual environment and highlight differences between younger and older adults. Drawn from these results, a discussion is included of needed robot capabilities, such as an approach that addresses varying perspectives used and recognition of furniture items for use as spatial references.

While highly constrained language can be used for robot control, robots that can operate as fully autonomous subordinate agents communicating via rich language remain an open challenge. Toward this end, we developed an autonomous system that supports natural, continuous interaction with the operator through language before, during, and after mission execution. The operator communicates instructions to the system through natural language and is given feedback on how each instruction was understood as the system constructs a logical representation of its orders. While the plan is executed, the operator is updated on relevant progress via language and images and can change the robot's orders. Unlike many other integrated systems of this type, the language interface is built using robust, general purpose parsing and semantics systems that do not rely on domain-specific grammars. This system demonstrates a new level of continuous natural language interaction and a novel approach to using general-purpose language and planning components instead of hand-building for the domain. Language-enabled autonomous systems of this type represent important progress toward the goal of integrating robots as effective members of human teams.