Abstract
Multimedia retrieval brings new challenges, mainly derived from the mismatch between the level of the user interaction-high-level concepts, and that of the automatically processed descriptors-low-level features. The effective use of the low-level descriptors is therefore mandatory. Many data structures have been proposed for managing the representation of multidimensional descriptors, each geared toward efficiency in some set of basic operations. The paper introduces a highly parametrizable structure called the BitMatrix, along with its search algorithms. The BitMatrix is compared with existing methods, all implemented in a common framework. The tests have been performed on two datasets, with parameters covering significant ranges of values. The BitMatrix has proved to be a robust and flexible structure that can compete with other methods for multidimensional descriptor indexing.

Abstract
Usage analysis of a Web Information System is a valuable help to predict user needs, to assess system's impact and to guide to its improvement. This is usually done analysing clickstreams, a low-level approach, with huge amounts of data that calls for data warehouse techniques. This paper presents a dimensional model to monitor user behaviour in Higher Education Web Information Systems and an architecture for the extraction, transformation and load process. These have been applied in the development of a data warehouse to monitor the use of SIGARRA, the University of Porto's Higher Education Web Information System. The efficiency and effectiveness of this monitorization method were confirmed by the knowledge extracted from a 3 month period analysis. A brief description of the main results and recommendations are also described.

Abstract
Good design and implementation are necessary but not sufficient pre-requisites for the successful reuse of object-oriented frameworks. Although not always recognized, good documentation is crucial for effective framework reuse but comes with many issues. Writing good quality documentation for a framework is often hard, costly, and tiresome, especially when not aware of its key problems and the best ways to address them. This document presents two of a set of related patterns that describe proven solutions to help non-experts on solving recurrent problems of documenting object-oriented frameworks. The patterns here presented address the problems of describing the customization points of the framework and how such customization is supported, respectively the patterns Customization Points and Design Internals. Copyright 2006 ACM.

Abstract
In the 2005 Portuguese Parliament General Elections there were non-valid experiments of e-voting at five voting places and also through the Internet. Faculdade de Engenharia da Universidade do Porto audited such experiments. Relevant security, transparency, usability and accessibility evaluation criteria and sub-criteria were defined, and an auditing procedure based on AHP was established. This paper shortly presents the methodology used, the four e-voting systems and the main results of the overall experiment. The systems could be used successfully and were extremely popular with voters. However, more information to the citizens and to the officials involved in the e-voting process would be required for a valid election. The systems also need to be improved, for instance, to make sure that the number of votes electronically cast is the same as the number of voters that were validated and actually registered to vote at any particular site on the Election Day.

Abstract
The Drag-And-Dock design pattern provides a structured solution for designing graphical software applications with multiple content views that end users can freely arrange following a dragging and docking interaction approach. Copyright 2006 ACM.

Abstract
A map can be a major advantage when exploring unfamiliar environments. With the proliferation of mobile devices, such as PDAs and even mobile phones, the tourist industry is currently exploring the potential of new presentation strategies that will maximize the promotional appeal of tourism in their region. Mobile devices are capable of guiding a tourist when he/she is exploring a city. These mobile devices offer the potential for providing relevant 3D information to enable tourists to locate themselves within the city, rapidly navigate around the unfamiliar environment and explore it interactively. However, the computational resources of current mobile technology prevents the display of full complex 3D content in real-time, and thus selective rendering techniques must be adopted to ensure the viewer is provided with the perceptually most important information at interactive rates. This paper presents a series of experiments which help to identify key features of a scene for users to orientate themselves in that environment. Knowledge of these salient key features enable them to be provided to a user at a high quality while the remainder of the scene can be rendered in a much lower quality, saving significant bandwidth and computing power, without the user being perceptually aware of this difference in quality within the image.