Abstract: The earliest design decisions often have a significant impact on software quality and are the most costly to revoke. One of the challenges in architecture design is to reduce the frequency of retrofit problems in software designs; not being able to improve the quality of a system cost effectively, a problem which frequently occurs during late stages. Software architecture assessment is essential in the design of a high quality system. However, assessing the effect of individual design decisions with respect to quality is often complicated by the fact that it is hard to identify exactly how particular qualities and quality factors are improved or impaired by design decisions. In this paper we present a framework that formalizes some of the relationships between software architecture and software quality; it compiles existing design knowledge (quality improving patterns) in a format suitable for architecture assessment. This framework may prevent the retrofit problem and can assist in reasoning about intra- and inter- quality tradeoffs. We illustrate our framework by creating an instance for it for the qualities usability, security and safety.

Abstract: Spider diagrams are a widely studied, visual logic that are able to make statements about relationships between sets and their cardinalities. Various meta-level results for spider diagrams have been established, including their soundness, completeness and expressiveness. In order to further enhance our understanding of spider diagrams, we can compare them with other languages; in the case of this paper we consider star-free regular languages. We establish relationships between various fragments of the spider diagram language and certain well-known subclasses of the star-free regular class. Utilising these relationships, given any spider diagram, we provide an upper-bound on the state complexity of minimal deterministic finite automata corresponding to that spider diagram. We further demonstrate cases where this bound is tight.

Abstract: In this paper we present the design and implementat io of an advanced virtual lab aimed at supporting teachin g a d learning in Computer Engineering courses. We first outline the requirements an educational tool must m eet to represent an effective and comprehensive support fo r students through the whole process that leads them to achieve conceptual understanding and technical skil ls. The described virtual lab, based on a constructivis t approach and suitable for use in blended-learning contexts, responds to a general model that allows i ts application in different educational domains. In th e second part of the paper we describe the implementa tio of vLab 2.0, a prototype built following the propos ed directions and the results of a prior experimentati on within the Information Security Technologies course hold at the Engineering Faculty of the University of Bol ogna. vLab 2.0 relies on Eclipse technology in order to guarantee openness and extensibility, and to access a set of advanced features which concur in providing supp ort for building a comprehensive and sophisticated tool f r teaching and learning.