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Abstract-Widespread adoption of Web technologies, particularly in professional and educational areas, has motivated new research efforts with the objective of designing new interaction mechanisms based on Web technologies. Within this framework, collaborative Web browsing (cobrowsing) aims at extending currently available Web browsing capabilities in order to allow several users to "browse together" on the Web. Such a browsing paradigm can have many useful applications, for instance, in e-learning, for collaboratively searching and retrieving documents, and for online assistance (helpdesk). A cobrowsing system should provide all the facilities required for allowing users to establish and release, in a very simple and flexible way, browsing synchronization relations as well as interactions with continuous media presentations embedded within Web pages. This paper presents the design, modeling, and implementation of the cobrowsing system called CoLab. CoLab provides all the functionalities required for allowing users to collaboratively browse the Web, and a first experimental version of the tool has been implemented and is fully operational.

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1Recent papers propose QoS solutions allowing the users to explicitly specify the quality level they request during a so-called explicit QoS service invocation that includes dynamic QoS offering and new mechanisms for authentication, authorization and accounting. In particular, organizations should be able to control their network services and authorize QoS services based on service parameters, as destination addresses, applications and employees' roles. Therefore, user profile-based authorization policies for explicit QoS service invocations should be adopted. Each user profile indicates the services that the user is authorized to request, their consumption limits and scope. This paper deals with the authorization of explicit QoS services invocations and proposes a user profile model for profile-based authorization of QoS services.

Abstract. Digital Libraries (DLs) usually provide facilities for browsing and searching their collections, and can enhance noticeably learning activities. The integration of an annotation tool with a DL can foster knowledge exchange between instructors and learners. It is important that an annotation system for DLs should be easily integrated with existing DLs. This paper presents an annotation system, called DLNotes, which can be easily embedded in DLs in order to enable free-text and ontology-based annotations. DLNotes also supports supervised annotation activities and allows discussion threads to be associated with each annotation, what is particularly important for e-learning.