Abstract
Wikis are popular tools commonly used to support distributed collaborative work. Wikis can be seen as virtual scrap-books that anyone can edit without having any specific technical know-how. The Wikipedia is a flagship example of a real-word application of wikis. Due to the large scale of Wikipedia it's difficult to easily grasp much of the information that is stored in this wiki. We address one particular aspect of this issue by looking at the revision history of each article. Plotting the revision activity in a timeline we expose the complete article's history in a easily understandable format. We present WIKICHANGES, a web-based application designed to plot an article's revision timeline in real time. WIKICHANGES also includes a web browser extension that incorporates activity sparklines in the real Wikipedia. Finally, we introduce a revisions summarization task that addresses the need to understand what occurred during a given set of revisions. We present a first approach to this task using tag clouds to present the revisions made. © 2008 ACM.

Abstract
While trying to understand and characterize users' behavior online, the temporal dimension has received little attention by the research community. This exploratory study uses two collections of web search queries to investigate the use of temporal information needs. Using state-of-the-art information extraction techniques we identify temporal expressions in these queries. We find that temporal expressions are rarely used (1.5% of queries) and, when used, they are related to current and past events. Also, there are specific topics where the use of temporal expressions is more visible.

Abstract
This paper presents the participation of FEUP, from University of Porto, in the TREC 2008 Blog Track. FEUP participated in two tasks, the baseline adhoc retrieval task and the blog finding distillation task. Our approach was focused on the use of the temporal information available in the TREC Blog06 collection. For the baseline adhoc retrieval task a simple temporal sort was evaluated. In the blog finding distillation task we tested three alternative scoring functions based on temporal evidence. All features were combined with a BM25 baseline run using a standard rank aggregation approach. We observed small, but statistically significant, improvements in several evaluation measures when temporal information is used.

Abstract
Nesting problems are particularly hard combinatorial problems. They involve the positioning of a set of small arbitrarily-shaped pieces on a large stretch of material, without overlapping them. The problem constraints are bidimensional in nature and have to be imposed on each pair of pieces. This all-to-all pattern results in a quadratic number of constraints. Constraint programming has been proven applicable to this category of problems, particularly in what concerns exploring them to optimality. But it is not easy to get effective propagation of the bidimensional constraints represented via finite-domain variables. It is also not easy to achieve incrementality in the search for an improved solution: an available bound on the solution is not effective until very late in the positioning process. In the sequel of work on positioning non-convex polygonal pieces using a CLP model, this work is aimed at improving the expressiveness of constraints for this kind of problems and the effectiveness of their resolution using global constraints. A global constraint "outside" for the non-overlapping constraints at the core of nesting problems has been developed using the constraint programming interface provided by Sicstus Prolog. The global constraint has been applied together with a specialized backtracking mechanism to the resolution of instances of the problem where optimization by Integer Programming techniques is not considered viable. The use of a global constraint for nesting problems is also regarded as a first step in the direction of integrating Integer Programming techniques within a Constraint Programming model.

Abstract
The widespread use of new technologies for data acquisition and communications is disclosing large amounts of time-varying data that organizations wish to use for monitoring or decision support purposes. The efficient management of such large data sets depends largely on the use of appropriate data structures and access methods. This issue is an important topic of research in the spatiotemporal databases community. This paper presents a novel approach for the representation of large series of time-varying multidimensional data. It is based on a model of approximations that allows creating a hierarchical data structure by using different degrees of precision for each level. The hierarchical data structure allows representing an instance of a single series of discretely or continuously changing data as an abstract data type. The paper also shows how to use this approach to represent the movement of an object within a spatiotemporal database system.

Abstract