People

Research activity in 1999

1. General Firing Time Distributions

   SPNs that include general firing time distributions are amenable to a preliminary structural analysis useful for validation, provided that the characteristics of these distributions are accounted for only at the time of the construction of the corresponding probabilistic models.

   The computation of performance and reliability evaluation indices from these representations requires the solution of problems that are either characterized by a complex probabilistic structure or by very large state spaces.

   These two different types of problems have been addressed by the group during this last year achieving the following results: General Firing Time distributions have also been implemented with the use of Fluid Stochastic Petri Nets with flush out arcs. Using this formalism, new and more complex memory polices are allowed. The use of tensor algebra has instead allowed to significantly enlarge the class of SPN with phase type dustribution for which it is possible to numerically compute an exact solution

2. Stochastic Process algebra

   Stochastic Process Algebras (SPA) represent an alternative method for modeling DEDS in which composition of basic modules is achieved by using proper construction operators.

   SPA models are often characterized by intrinsic symmetries that make them comparable with Petri net based representations developed with the use of Stochastic Well Formed Petri Nets (SWN).

   In this year we have addresses the problem of the use of process algebras for diagnosis problems and the study of the expressiveness of stochastic process algebras with respect to stochastic Petri nets

3. Solution of SPNs and SWNs

   Bounds for SPN, and, more generally, for CTMC have been developed, based on stochastic ordering

   The tensor based solution for GSPN has been extended to include synchronization of components over immediate actions: this has allowed a significant enlargment of the application that can benefit of the efficiency of tensor based analysis

   Product form algorithms for a class of SPN, and for a restrict class of queueing networks with blocking have been developed: these algorithms can be used for the computation of performance measures for product form models as well as for computing approximate measures for non-product form models.

4. Applications

   GSPNs and SWN have been extensively used during this year for the analysis of problems coming from different application fields.

   GSPN and SWN have been used inside the european project TIRAN to evaluate a software solution to fault tolerance in embedded systems: models have been used to evaluate the correctness of the fault tolerant function proposed, as well as the impact on the performability of the applications that use the functions.

   Modeling and analysis of ATM network components by means of GSPN and SWN models: the approach is based on the use of a single timed transition that acts as the master clock and several immediate transitions representing the system activities; the obtained stochastic process is a Continuous Time Markov Chain that is efficiently analyzed.

   Exact and approximate computation of the performance measures for cellular communication networks: in this case the models are very large and hence the availability of efficient algorithms for the computation of the performance measures (exact and approximate) is a necesary condition for the analysis of this kind of communication networks.

5. High-Level Fault Trees

   Development of the formalism called "High-Level Fault Trees" (HLFT) to support dependability analysis of safety-critical systems. Based on the observation that high dependability is obtained through replication that induces symmetries in the system layout a new algorithm is provided that translates a HLFT into a SWN; quantitative and qualitative analysis of the resulting model are then carried out exploiting efficient algorithms already developed for SWN.

6. Fluid Stochastic Petri Nets

   The basic model of Fluid Stochastic Petri Nets, has been extended adding a new primitive called flush-outs. Equations for this new formalism have been derived, and new analytical, numerical and simulative technique have been introduced. The proposed formalism has been used to analyze software system with checkpointing, rejuvenation and self-restoration, and it has been demonstrated being capable of including non-markovian Petri nets.

1999 Publications

J. Campos, S. Donatelli, and M. Silva. Structured Solution of Asynchronously Communicating Stochastic Modules. In IEEE Transactions on Software Engineering, 25(2), April 1999.

S. Donatelli and editors J. Kleijn, editors. Proceedings 20^th International Conference Application and Theory of Petri Nets. Springer Verlag, Vol. 1639, Williamsburgh, June 1999.

S. Donatelli, S. Haddad, P.Moreaux, and M. Sene. Bounds for rewards of systems with client/server interaction. In B. Plateau, W. Stewart, and M. Silva, editors, in Proceedings of Numerical solution of Markov Chain 1999. Zaragoza (Spagna), September 1999. B. Plateau, W. Stewart and M. Silva Editors.

M. Ajmone Marsan, S. Donatelli, G. Franceschinis, and F. Neri. Reductions in GSPN and SWN: an Overview and an Example of Application. In K. Bagchi, J. Walrand, and G.W. Zobrist, editors, in the monograph "State of the Art in Performance Modelling and Simulation: Network Theory, Tools and Tutorials”. K. Bagchi, J. Walrand and G.W. Zobrist editors, Gordon and Breach Publisher, 1999, pp. 56-95

M. Ajmone Marsan and R.Gaeta. “GSPN and SWN Models for ATM”. In Proceedings of Workshop on Formal Methods and Telecommunications (WFMT 99), Zaragoza, Spain, September 1999, pp.137-156.

A. Bobbio, G. Franceschinis, R. Gaeta, L. Portinale. “Exploiting Petri Nets to Support Fault Tree Based Dependability Analysis”. In Proceedings of 8^th International Workshop on Petri Nets and Performance Models (PNPM), IEEE-CS Press. Zaragoza, Spain, September 1999, pp.146-155.

L. Capra, R. Gaeta, and O. Botti. “SWN Nets as a Framework for the Specification and the Analysis of FT Techniques Adopted in Electric Plant Automation”. , Proceedings of 20th International Conference on Application and Theory of Petri Nets, Williamsburgh, Springer-Verlag, June 1999. In LNCS n.1639, Susanna Donatelli and Jetty Kleijn (Eds.), pp.168-187.

S. Gilmore, J. Hillston, and M. Ribaudo. An Efficient Algorithm for Aggregating PEPA Models. University of Edinburgh. Submitted to IEEE Transactions of Software Engineering, 1999.

M. Ajmone Marsan, M. Meo, and M. Sereno. GSPN Analysis of Dual-Band Mobile Telephony Networks. In Proceedings 8^th International Workshop on Petri Nets and Performance Models (PNPM ’99), Zaragoza, Spain, 8-10 September 1999. IEEE-CS Press, pages 54-63.

A. Bobbio, S. Garg, M. Gribaudo, A. Horváth, M. Sereno, and M. Telek. Modeling Software Systems with Rejuvenation, Restoration and Checkpointing through Fluid Stochastic Petri Nets. In Proceedings 8^th International Workshop on Petri Nets and Performance Models (PNPM ’99), Zaragoza, Spain, 8-10 September 1999. IEEE-CS Press. pages 82-91.

M. Gribaudo, M. Sereno, and A. Bobbio. Fluid Stochastic Petri Nets: An Extended Formalism to Include non-Markovian Models. In Proceedings 8^th International Workshop on Petri Nets and Performance Models (PNPM ’99), Zaragoza, Spain, 8-10 September 1999. IEEE-CS Press. pages 74-81B.

M. Sereno. Mean value analysis of product form solution queueing networks with repetitive service blockingmean. Atti della Conferenza Performance 99, Performance Evaluation, pages 19-33, 1-4 1999.

E. Teruel, G. Franceschinis and M. De Pierro. Clarifying the Priority Specification of GSPN: Detached Priorities. In Proceedings 8^th International Workshop on Petri Nets and Performance Models, Zaragoza, Spain, September 1999, pages 114-123.

L. Capra, C. Dutheillet, G. Franceschinis and J.M. Iliè. Towards Performance Analysis with Partially Symmetrical SWN. In Proceedings 7^th International Symposium on Modeling, Analysis and Simulation, College Park, MD, USA, October 1999, pp. 67-86

Activity and role in the scientific community

• Member of the Editorial Board of the International Journal of Computer System Science and Engineering, CRL Publishing Ltd. Leics, U.K.


• Member of the IFIP Working Group 7.3 "Information Processing System Modeling, Measurement and Evaluation"


• Member of the Steering Committee of the "International Conference on Applications and Theory of Petri Nets"


• Member of the Steering Committee of the "IEEE International Computer Performance and Dependability Symposium"


• Member of the Program Committee of the "8-th Intern. Workshop on Petri Nets and Performance Models, PNPM’99”, Zaragoza, Spain, September 1999.


• Chairman of the Tutorial Program of the “Multi-Workshop on Formal Methods in Performance Evaluation and Applications”, Zaragoza, Spain, September 1999.


• Organizer and Speaker of the “Advanced Tutorial on Performance Analysis” of the “”20-th Inetrn. Conference on Application and Theory of Petri Nets, ICATPN’99”, Williamsburg, USA, June 1999.


• Lecturer of the "National Computer Science Graduate School, SNDIS’99”, University of Bologna, Bertinoro, Italy, May 1999.


• Referee for the following international Journals: Performance Evaluation, European Journal of Operation Research, Science of Computer Programming.


• Referee for the following international conferences: International Workshop on Petri Nets and Performance Models (PNPM’99), 7-th International Symposium on Modelling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS’99).


• Referee for the Research Proposal “The Virtual Enterprise: An Interactive Distributed Collaborative Work Environment” submitted by Prof. Alois Ferscha of the University of Vienna to the Austrian National Bank Research Sponsoring Agency


• Member of the Evaluation Committee for the degree “Diplome d’Abilitation a Diriger des Recherches” of Mohamed Kaaniche, Institute National Polytechnique de Toulouse, France.

• Program Chairman of:
  
  • 20^th International Conference, ICATPN 99, June 1999, Williamsburg, Virginia, USA.
  
  
• Program Committee of:
  
  • 8^th International Workshop on Petri Nets and Performance Models (PNPM),
  
  
• Referee:
  
  • 7^th International Workshop on Process Algebra and Performance Modelling (PAPM)
  
  
  • Modellig Techniques and Tools for Computer Performance Evaluation 2000
  
  
  • 8^th International Workshop on Petri Nets and Performance Models (PNPM),
  
  
  • 20^th International Conference, ICATPN 99, June 1999, Williamsburg, Virginia, USA.
  
  
  • Tools and Algorithms for the Construction and Analysis of Systems (TACAS 99)
  
  
  • Numerical Solution of Markov Chains (NSMC ’99)
  
  
• Thesis Committee:
  
  • “Rapporteur” of the PhD Moohsan Zouaoui
  
  

• Program Committee:
  
  • 7^th International Workshop on Process Algebra and Performance Modelling (PAPM)
  
  
• Referee for the following international conferences:
  
  • 7^th International Workshop on Process Algebra and Performance Modelling (PAPM)
  
  
  • Modellig Techniques and Tools for Computer Performance Evaluation 2000
  
  
  • Tools and Algorithms for the Construction and Analysis of Systems (TACAS 2000)
  
  
• Referee for the following international journals:
  
  • Journal of System and Automation
  
  

• Referee for the following international conferences:
  
  • 8^th International Workshop on Petri Nets and Performance Models (PNPM),
  
  
  • 7^th International Workshop on Process Algebra and Performance Modelling (PAPM)
  
  
• Referee for the following international journals:
  
  • Performance Evaluation
  
  

Oral Presentations in Congresses and Conferences

• Structured solutions Methods for GSPN with Phase Type Distributions: Multi-Conference on Performance Evaluation (PNPM 99 – PAPM 99 – NSMC 99)


• Two hours tutorial on Storage and Analysis Techniques for Tensor Based Solutions: 20^th International Conference, ICATPN 99, June 1999, Williamsburg, Virginia, USA


• Two hours tutorial on introduction to GSPN: 20^th International Conference, ICATPN 99, June 1999, Williamsburg, Virginia, USA.

• 20^th International Conference, ICATPN 99, June 1999, Williamsburg, Virginia, USA.


• 8^th International Workshop on Petri Nets and Performance Models (PNPM), Zaragoza, Spain, September 1999.


• Workshop on Formal Methods and Telecommunications (WFMT 99), Zaragoza, Spain, September 1999.

• Presentation of the paper: “Fluid Stochastic Petri Nets: An Extended Formalism to Include non-Markovian Models” during the “International Workshop on {Petri} Nets and Performance Models 1999, PNPM'99” held in Zaragoza (Spain), september 1999.