The Leavitt path algebra of a graph

For any row-finite graph $E$ and any field $K$ we construct the {\its Leavitt path algebra} $L(E)$ having coefficients in $K$. When $K$ is the field of complex numbers, then $L(E)$ is the algebraic analog of the Cuntz Krieger algebra $C^*(E)$ described in [8]. The matrix rings $M_n(K)$ and the Leavitt algebras L(1,n) appear as algebras of the form $L(E)$ for various graphs $E$. In our main result, we give necessary and sufficient conditions on $E$ which imply that $L(E)$ is simple

Purely infinite simple Leavitt path algebras

We give necessary and sufficient conditions on a row-finite graph E so that the Leavitt path algebra L(E) is purely infinite simple. This result provides the algebraic analog to the corresponding result for the Cuntz-Krieger C$^*$-algebra C$^*$(E) given in [7]

Finding secure compositions of software services: Towards a pattern based approach

In service based systems, there is often a need to replace services at runtime as they become either unavailable or they no longer meet required quality or security properties. In such cases, it is often necessary to build compositions of services that can replace a problematic service because no single service with a sufficient match to it can be located. In this paper, we present an approach for building compositions of services that can preserve required security properties. Our approach is based on the use of secure composition patterns which are applied in connection with basic discovery mechanisms to build secure service compositions

Constructing secure service compositions with patterns

In service based applications, it is often necessary to construct compositions of services in order to provide required functionality in cases where this is not possible through the use of a single service. Whilst creating service compositions, it is necessary to ensure not only that the functionality required of the composition is achieved but also that certain security properties are preserved. In this paper, we describe an approach to constructing secure service compositions. Our approach is based on the use of composition patterns and rules that determine the security properties that should be preserved by the individual services that constitute a composition in order to ensure that security properties of the overall composition are also satisfied. Our approach extends a framework developed to support the runtime service discovery

Conflictos entre derechos fundamentales. Una cr\uedtica a Luigi Ferrajoli

This essay deals with a specific \u2013 but by no means marginal \u2013 feature of the complex and rich theory of fundamental rights developed by Luigi Ferrajoli, the problem of conflicts of rights. To begin with, I will draw a quite generic theoretical framework about (at least prima facie, or potential) conflicts between fundamental rights in the context of contemporary constitutional states. Then I will describe Luigi Ferrajoli\u2019s thesis about the absence, or at least the very marginal role of conflicts between fundamental rights. Conclusively, I will point to some possible critiques to the strategy elaborated by Ferrajoli in order to reduce the impact of conflicts between fundamental rights

Diritti soggettivi. Lineamenti di un'analisi teorica

il saggio analizza il concetto di diritto soggettico, con riferimento alla struttura (Hohfeld) e al fondamento dei diritti (Interest Theory v. Will Theory