Automatic symmetry detection in well-formed nets

Abstract. Formal verification of complex systems using high-level Petri Nets faces the so-called state-space explosion problem. In the context of Petri nets generated from a higher level specification, this problem is particularly acute due to the inherent size of the considered models. A solution is to perform a symbolic analysis of the reachability graph, which exploits the symmetry of a model. Well-Formed Nets (WN) are a class of high-level Petri nets, developed specifically to allow automatic construction of a symbolic reachability graph (SRG), that represents equivalence classes of states. This relies on the definition by the modeler of the symmetries of the model, through the definition of “static sub-classes”. Since a model is self-contained, these (a)symmetries are actually defined by the model itself. This paper presents an algorithm capable of automatically extracting the symmetries inherent to a model, thus allowing its symbolic study by translating it to WN. The computation starts from the assumption that the model is entirely symmetric, then examines each component of a net to deduce the symmetry break it induces. This translation is transparent to the end-user, and is implemented as a service for the AMI-Net package. It is particularly adapted to models containing large value domains, yielding combinatorial gain in the size of the reachability graph.

Resource management with X.509 inter-domain authorization certificates (InterAC)

Collaboration among independent administrative domains would require: i) confidentiality, integrity, non-repudiation of communication between the domains; ii) minimum and reversible modifications to the intra-domain pre-collaboration setup; iii) maintain functional autonomy while collaborating; and, iv) ability to quickly transform from post-collaboration to pre-collaboration stage. In this paper, we put forward our mechanism that satisfies above requirements while staying within industry standards so that the mechanism becomes practical and deployable. Our approach is based on X.509 certificate extension. We have designed a non-critical extension capturing users' rights in such a unique way that the need for collaboration or the post-collaboration stage does not require update of the certificate. Thus, greatly reducing the revocation costs and size of CRLs. Furthermore, rights amplification and degradation of users from collaborating domains into host domain can be easily performed. Thus, providing functional autonomy to collaborators. Initiation of collaboration among two domains require issuance of one certificate from each domain and revocation of these certificates ends the collaboration - ease of manageability. © 2010 Springer-Verlag

Resource Management with X.509 Inter-domain Authorization Certi\ufb01cates (InterAC)

Collaboration among independent administrative domains would require: i) confidentiality, integrity, non-repudiation of communication between the domains; ii) minimum and reversible modifications to the intra-domain precollaboration setup; iii) maintain functional autonomy while collaborating; and, iv) ability to quickly transform frompost-collaboration to pre-collaboration stage. In this paper, we put forward our mechanism that satisfies above requirements while staying within industry standards so that the mechanism becomes practical and deployable. Our approach is based on X.509 certificate extension. We have designed a non-critical extension capturing users' rights in such a unique way that the need for collaboration or the post-collaboration stage does not require update of the certificate. Thus, greatly reducing the revocation costs and size of CRLs. Furthermore, rights amplification and degradation of users from collaborating domains into host domain can be easily performed. Thus, providing functional autonomy to collaborators. Initiation of collaboration among two domains require issuance of one certificate from each domain and revocation of these certificates ends the collaboration - ease of manageability

Impact of electric cars deployment on the Italian energy system

Electric vehicles are supposed to play a leading role in the transition towards a low carbon society since they allow to substitute oil products with electricity as the main energy source for transportation. On the other hand, the diffusion of electric vehicles determines an increase in power demand with a consequent variation in the power supply mix. In accordance with this, it is mandatory to analyse how the supply mix changes, since the introduction of electric vehicles is significant from the sustainability point of view only if there is a reduction in emissions. To assess this condition for the Italian energy system, the present paper proposes a model developed in EnergyPLAN. Three different scenarios are tested in terms of the penetration of electric vehicles to understand which is the optimal trajectory for their diffusion. The analysis demonstrates that the Italian energy system can accommodate 7 million electric cars, namely about 25% of the total in 2040. A higher amount would determine an increase in carbon emissions

GAMMA on DEC 2114x with Efficient Flow Control

GAMMA is a prototype light-weight communication system based on the Active Ports paradigm, designed for efficient implementation over Fast Ethernet interconnects. The original implementation started in 1996 based on 3Com 3C595 cards. The optimizations obtained on that NICs allowed us to obtain the lowest latency and highest throughput results ever published in the literature for Fast Ethernet. Technology evolved, however, and now all low-cost NICs available are based on Descriptor Based DMA (DBDMA) transfers, originally introduced by the DEC chipset 21140. In this paper we report on the re-implementation of the GAMMA prototype for the DEC NICs exploiting the new transfer modes and achieving substantially equivalent performance figures. We also describe the addition of an efficient flow-control algorithm, that allows loss-free communications without seriously affecting performance. Keywords: Active Ports; Fast Ethernet; Low Latency; Descriptor Based DMA; Flow-control. 1 Introduction Li..

Optimizing the finger tables in Chord-like DHTs

The Chord protocol is the best known example of implementation of logarithmic complexity routing for structured peer-to-peer networks. Its routing algorithm, however, does not provide an optimal trade-off between resources exploited (the size of the ``finger table'') and performance (the average or worst-case number of hops to reach destination). Cordasco et al. showed that a finger table based on Fibonacci distances provides lower number of hops with fewer table entries. In this paper we generalize this result, showing how to construct an improved finger table when the objective is to reduce the number of hops, possibly at the expense of an increased size of the finger table. Our results can also be exploited to guarantee low routing time in case a fraction of nodes fails