Francesco Di Cerbo

Extreme Apprenticeship Goes Blended: An Experience

The paper describes the eXtreme Apprenticeship methodology and its application inside a blended laboratory on Operating Systems. Extreme Apprenticeship is based on Cognitive Apprenticeship: apprentices learn a task by first observing the master performing it, and then practising under master guidance. The role of a Learning Management System in scaffolding apprentices is underlined, and some preliminary evaluation of the experience is presented.

A precise style for business process modelling: results from two controlled experiments

We present a precise style for the modelling of business processes based on the UML activity diagrams and two controlled experiments to compare this style with a lighter variant. The comparison has been performed with respect to the comprehensibility of business processes and the effort to comprehend them. The first experiment has been conducted at the Free University of Bolzano-Bozen, while the second experiment (i.e., a differentiated replication) at the University of Genova. The participants to the first experiment were Master students and so more experienced than the participants to the replication, who were Bachelor students. The results indicate that: (a) all the participants achieved a significantly better comprehension level with the precise style; (b) the used style did not have any significant impact on the effort; and (c) more experienced participants benefited more from the precise style.

On the comprehension of workflows modeled with a precise style: results from a family of controlled experiments

In this paper, we present the results from a family of experiments conducted to assess whether the level of formality/precision in workflow modeling, based on UML activity diagrams, influences two aspects of construct comprehensibility: correctness of understanding and task completion time. In particular, we have considered two styles for workflow modeling with different levels of formality: a precise style (with specific rules and imposed constraints) and an ultra-light style (no rules, no imposed constraints). Experiments were conducted with 111 participants (Bachelor and Master students). In each experiment, participants accomplished comprehension tasks on two workflows, modeled either with the precise style or with a lighter variant. The main results from our data analysis can be summarized as follows: (i) all participants achieved a significantly better comprehension of workflows written in the precise style, (ii) the style had no significant impact on task completion time, (iii) more experienced participants benefited more, with respect to less experienced ones, from the precise style, as for their correctness of understanding, and (iv) all participants found the precise style useful in comprehending workflows.

Balancing Trust and Risk in Access Control

The increasing availability of large and diverse datasets big data calls for increased flexibility in access control so to improve the exploitation of the data. Risk-aware access control systems offer a natural approach to the problem. We propose a novel access control framework that combines trust with risk and supports access control in dynamic contexts through trust enhancement mechanisms and risk mitigation strategies. This allows to strike a balance between the risk associated with a data request and the trustworthiness of the requester. If the risk is too large compared to the trust level, then the framework can identify adaptive strategies leading to a decrease of the risk e.g., by removing/obfuscation part of the data through anonymization or to increase the trust level e.g., by asking for additional obligations to the requester. We outline a modular architecture to realize our model, and we describe how these strategies can be actually realized in a realistic use case.

Bridging the Gap between PLE and LMS

Learning Management Systems (LMS) represent todays preferred technology for institutional e-learning. Unfortunately, they show poor adaptability to each users needs, and learners may suffer from the walled garden effect. Many researchers are investigating the Personal Learning Environment (PLE) as a way to overcome such limitations, fostering a lifelong learning perspective. In this paper we propose to extend a LMS, namely DIEL, to unify the benefits of LMS and PLE, supporting better learning experiences and processes. Experiences with the first prototype are also briefly summarized.

PPL v2.0: uniform data access and usage control on cloud and mobile

Cloud storage is one of the most popular categories of market services. It provides an easy means for consumers to store and share their data, also in mobility through convenient apps. However, such valuable functionality raises several security concerns. Among them, the risk of sensitive information disclosure or, for professional data, the risk of compliance violations. In this paper, we propose an access and usage control framework for seamless, uniform and secure data sharing across cloud and mobile which keeps data under the control of its owner, that expresses preferences according to privacy or security needs. To our knowledge, this is the first effort addressing simultaneously and consistently cloud and mobile platforms. Our proposal offers access and usage control of managed resources relying on the security policy languages XACML and PPL (extended to make use of cloud and mobile contextual information) and on specific engines (cloud, mobile) to enforce them. A use case is presented, to illustrate the framework in action.

Optimizing Access Control Performance for the Cloud

Cloud computing is synonym of high performance computing. It offers a very scalable infrastructure to deploy a huge number of systems and services without any impact of the performance. Such a wide distributed infrastructure, as for the traditional systems, requires authorization and access control mechanisms to ensure the basic security requirements to restrict the access to resources. To satisfy these requirements cloud providers still rely on the traditional authorization and access control systems that in some critical cases can generate performance issues. More the access control structure is complex (many authorization levels, many users and resources to protect), more the enforcement of the access control policies is slow. In this paper we propose a performance study for these traditional access control mechanisms demonstrating the overhead generated by the authorizations checking that can appear in extreme usage conditions. We propose a new approach to make access control systems more scalable and adapted to cloud computing high performance requirements. This approach is based on a high speed caching access control tree that accelerates the decision without impacting on the consistency of the rules. We compare the performance test results obtained by our solution to a traditional Access control system deployed in the cloud.

Social Networking Technologies for Free-Open Source E-Learning Systems

In this paper, we illustrate our methodology for academic teaching, based on cooperative learning paradigm, which also relies on cutting edge e-learning techniques. We use Web 2.0 resources to fulfill requirements for an interactive-constructivistic “learning space”, where blended-teaching paradigm may be proficiently applied. We extend an existing Free/Open Source Software Learning Management System, to create a cooperative and community-based learning space adherent to our proposal.

DULP Perspectives in a Learning Management System

The DULP vision is providing an innovative perspective for rethinking learning processes, to become, among the others, ubiquitous and focused on persons in place-centred design, according to the new reality that we face every day. The challenge we present today is to bring the DIEL system further into exploring DULP-provided possibilities, with a specific effort on mobile learning and in the exploration of the meanings of quantitative data collection as indicators of the learning process trends.

Extending moodle for collaborative learning

In this demo, we present novel features added to the Moodle Learning Management System to achieve collaborative learning