Darío Álvarez Gutiérrez

Sirius: A heuristic-based framework for measuring web usability adapted to the type of website

The unquestionable relevance of the web in our society has led to an enormous growth of websites offering all kinds of services to users. In this context, while usability is crucial in the development of successful websites, many barely consider the recommendations of experts in order to build usable designs. Including the measurement of usability as part of the development process stands out among these recommendations. One of the most accepted methods for usability evaluation by experts is heuristic evaluation. There is abundant literature on this method. However, there is a lack of clear and specific guidelines to be used in the development and evaluation process. This is probably an important factor contributing to the aforementioned generalized deficiency in web usability. We miss an evaluation method based on heuristics whose measure is adapted to the type of evaluated website. In this paper we define Sirius, an evaluation framework based on heuristics to perform expert evaluations that takes into account different types of websites. We also provide a specific set of evaluation criteria, and a usability metric that quantifies the usability level achieved by a website depending on its type.

An Object-Oriented Abstract Machine as the Substrate for an Object-Oriented Operating System

Using an object-oriented abstract machine brings a number of benefits for the construction of an object-oriented operating system. In this paper we describe the structure of an abstract machine designed for this task. This machine provides the basic object model and support for the rest of the system. Among other options, we propose a reflective architecture as a collaboration mechanism between the machine and the OS. Finally, we show how using this architecture based on the abstract machine improves and facilitates the construction of operating system features like orthogonal persistence, object distribution, concurrency and capability-based security, giving a flexible integral OO computing environment.

Merging Capabilities with the Object Model of an Object-Oriented Abstract Machine

The evolution towards heterogeneous distributed interoperable objects multiplies the need to have robust fine-grained object protection mechanisms in order to allow only authorized method invocations. Oviedo3 [1] is an example of these kind of Object-Oriented Integral Systems (IOOS) based solely on the OO paradigm. A reflective OO Abstract Machine (OOAM) is coupled with an OO operating system composed of a set of user objects providing OS functionality.

Applying lightweight flexible virtual machines to extensible embedded systems

Virtual Machines are spreading from the desktop to other domains. Embedded Systems is a domain where the benefits of Virtual Machines such as portability or software-based isolation can be of much help. However, for highly dynamical, extensible systems we believe that the key features needed in a VM to succeed in the domain are flexibility and lightweightness, and that reflection and a VM reduced instruction set are the means to achieve this. In this paper we briefly describe two VMs built in our research group with the before mentioned properties that could be evolved for the embedded systems domain: The Carbayonia and the nitrO Abstract Machines.

A Fast Data Protection Technique for Mobile Agents to Avoid Attacks in Malicious Hosts

Abstract Mobile agents have been considered a promising technology to develop e-commerce applications, however the security concerns about the technology have stopped its widespread use. The identified security areas comprise protecting hosts against malicious agents, protecting the agents transmission and protecting agents against malicious hosts. The first two security issues and the protection of the code state of the agent can be solved by applying traditional security techniques. Even though there are some works that manage the data state protection, its implementation is almost unfeasible in terms of performance and complexity. This paper describes a fast and easy to implement algorithm that a mobile agent can use to encrypt its data during its itinerary. The algorithm only makes use of a bitmap and XOR operations. The algorithm consist of applying XOR operations to the data to be ciphered and a random bitmap, while the map is repeatedly shifted to the right or to the left in order to compute a CRC field for validation against malicious tampering. The method only uses basic bit operations so that its implementation is very easy to develop. Besides, since it does not use any computationally expensive cryptographic technique (i.e. digital signatures) it is very fast. In this way we manage to have a secure, simple, fast and feasible protection algorithm to protect data while mobile agents are roaming, where simplicity and performance are its better advantages.

4th Workshop on OO and Operating Systems

The workshop aims to bring together researchers and developers working on object-oriented operating systems and to provide a platform for discussing problems arising from the application of object-orientation to operating systems and solutions for them. Suggested topics for position papers and discussions include, but are not restricted to: adaptable and adaptive OOOS, frameworks for OOOS, architecture of OOOS, distributed OOOS and middleware, aspect orientation and OOOS design, what are the penalties of OO in OS and how to avoid them, reflective OOOS, OOOS tools, reusability and interoperability of OOOS components, OOOS configurability, maintenance, tuning and optimization, OOOS for embedded systems, real-time OOOS.

Capability-based protection for integral object-oriented systems

Protection is an essential issue for the heterogeneous distributed interoperable environments, which Java and CORBA are a glimpse of. A uniform protection mechanism such as capabilities integrated with the object model of the system is a good and flexible solution for these environments. Oviedo3 is an example of an integral object oriented system (IOOS) based solely on the OO paradigm, developed over an OO abstract machine (OOAM) and OO operating system (OOOS). When integrated with the object model of the abstract machine, capabilities gain new advantages such as automatic protection. Capabilities also allow more flexible security policies. Existing platforms such as Java, without a uniform protection mechanism, could be made more suitable for these new environments by applying these benefits.