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Author |
Della Penna, Giuseppe; Intrigila, Benedetto; Melatti, Igor; Tronci, Enrico; Venturini Zilli, Marisa |
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Title |
Finite Horizon Analysis of Stochastic Systems with the Mur$\varphi$ Verifier |
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Conference Article |
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2003 |
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Theoretical Computer Science, 8th Italian Conference, ICTCS 2003, Bertinoro, Italy, October 13-15, 2003, Proceedings |
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58-71 |
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Many reactive systems are actually Stochastic Processes. Automatic analysis of such systems is usually very difficult thus typically one simplifies the analysis task by using simulation or by working on a simplified model (e.g. a Markov Chain). We present a Finite Horizon Probabilistic Model Checking approach which essentially can handle the same class of stochastic processes of a typical simulator. This yields easy modeling of the system to be analyzed together with formal verification capabilities. Our approach is based on a suitable disk based extension of the Mur$\varphi$ verifier. Moreover we present experimental results showing effectiveness of our approach. |
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Springer |
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Blundo, C.; Laneve, C. |
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Lecture Notes in Computer Science |
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2841 |
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3-540-20216-1 |
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yes |
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Sapienza @ mari @ DIMTZ03c |
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90 |
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Author |
Della Penna, Giuseppe; Intrigila, Benedetto; Melatti, Igor; Tronci, Enrico; Venturini Zilli, Marisa |
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Title |
Bounded Probabilistic Model Checking with the Mur$\varphi$ Verifier |
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Conference Article |
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Year |
2004 |
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Formal Methods in Computer-Aided Design, 5th International Conference, FMCAD 2004, Austin, Texas, USA, November 15-17, 2004, Proceedings |
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214-229 |
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In this paper we present an explicit verification algorithm for Probabilistic Systems defining discrete time/finite state Markov Chains. We restrict ourselves to verification of Bounded PCTL formulas (BPCTL), that is, PCTL formulas in which all Until operators are bounded, possibly with different bounds. This means that we consider only paths (system runs) of bounded length. Given a Markov Chain $\cal M$ and a BPCTL formula Φ, our algorithm checks if Φ is satisfied in $\cal M$. This allows to verify important properties, such as reliability in Discrete Time Hybrid Systems. We present an implementation of our algorithm within a suitable extension of the Mur$\varphi$ verifier. We call FHP-Mur$\varphi$ (Finite Horizon Probabilistic Mur$\varphi$) such extension of the Mur$\varphi$ verifier. We give experimental results comparing FHP-Mur$\varphi$ with (a finite horizon subset of) PRISM, a state-of-the-art symbolic model checker for Markov Chains. Our experimental results show that FHP-Mur$\varphi$ can effectively handle verification of BPCTL formulas for systems that are out of reach for PRISM, namely those involving arithmetic operations on the state variables (e.g. hybrid systems). |
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Springer |
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Hu, A.J.; Martin, A.K. |
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Lecture Notes in Computer Science |
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Series Volume |
3312 |
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3-540-23738-0 |
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yes |
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Sapienza @ mari @ Dimtz04 |
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87 |
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Author |
Della Penna, Giuseppe; Intrigila, Benedetto; Melatti, Igor; Tronci, Enrico; Venturini Zilli, Marisa |
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Title |
Exploiting Transition Locality in Automatic Verification of Finite State Concurrent Systems |
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Journal Article |
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Year |
2004 |
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Sttt |
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6 |
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4 |
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320-341 |
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In this paper we show that statistical properties of the transition graph of a system to be verified can be exploited to improve memory or time performances of verification algorithms. We show experimentally that protocols exhibit transition locality. That is, with respect to levels of a breadth-first state space exploration, state transitions tend to be between states belonging to close levels of the transition graph. We support our claim by measuring transition locality for the set of protocols included in the Mur$\varphi$ verifier distribution. We present a cache-based verification algorithm that exploits transition locality to decrease memory usage and a disk-based verification algorithm that exploits transition locality to decrease disk read accesses, thus reducing the time overhead due to disk usage. Both algorithms have been implemented within the Mur$\varphi$ verifier. Our experimental results show that our cache-based algorithm can typically save more than 40% of memory with an average time penalty of about 50% when using (Mur$\varphi$) bit compression and 100% when using bit compression and hash compaction, whereas our disk-based verification algorithm is typically more than ten times faster than a previously proposed disk-based verification algorithm and, even when using 10% of the memory needed to complete verification, it is only between 40 and 530% (300% on average) slower than (RAM) Mur$\varphi$ with enough memory to complete the verification task at hand. Using just 300 MB of memory our disk-based Mur$\varphi$ was able to complete verification of a protocol with about $10^9$ reachable states. This would require more than 5 GB of memory using standard Mur$\varphi$. |
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yes |
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Call Number |
Sapienza @ mari @ DIMTZ04j |
Serial |
91 |
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Author |
Della Penna, Giuseppe; Intrigila, Benedetto; Melatti, Igor; Tronci, Enrico; Venturini Zilli, Marisa |
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Title |
Finite horizon analysis of Markov Chains with the Mur$\varphi$ verifier |
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Journal Article |
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2006 |
Publication |
Int. J. Softw. Tools Technol. Transf. |
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8 |
Issue |
4 |
Pages |
397-409 |
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In this paper we present an explicit disk-based verification algorithm for Probabilistic Systems defining discrete time/finite state Markov Chains. Given a Markov Chain and an integer k (horizon), our algorithm checks whether the probability of reaching an error state in at most k steps is below a given threshold. We present an implementation of our algorithm within a suitable extension of the Mur$\varphi$ verifier. We call the resulting probabilistic model checker FHP-Mur$\varphi$ (Finite Horizon Probabilistic Mur$\varphi$). We present experimental results comparing FHP-Mur$\varphi$ with (a finite horizon subset of) PRISM, a state-of-the-art symbolic model checker for Markov Chains. Our experimental results show that FHP-Mur$\varphi$ can handle systems that are out of reach for PRISM, namely those involving arithmetic operations on the state variables (e.g. hybrid systems). |
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Springer-Verlag |
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Berlin, Heidelberg |
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1433-2779 |
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yes |
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Call Number |
Sapienza @ mari @ Dimtz06 |
Serial |
78 |
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Author |
Mari, Federico; Tronci, Enrico |
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Title |
CEGAR Based Bounded Model Checking of Discrete Time Hybrid Systems |
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Conference Article |
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Year |
2007 |
Publication |
Hybrid Systems: Computation and Control (HSCC 2007) |
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399-412 |
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Model Checking, Abstraction, CEGAR, SAT, Hybrid Systems, DTHS |
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Many hybrid systems can be conveniently modeled as Piecewise Affine Discrete Time Hybrid Systems PA-DTHS. As well known Bounded Model Checking (BMC) for such systems comes down to solve a Mixed Integer Linear Programming (MILP) feasibility problem. We present a SAT based BMC algorithm for automatic verification of PA-DTHSs. Using Counterexample Guided Abstraction Refinement (CEGAR) our algorithm gradually transforms a PA-DTHS verification problem into larger and larger SAT problems. Our experimental results show that our approach can handle PA-DTHSs that are more then 50 times larger than those that can be handled using a MILP solver. |
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Springer |
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Bemporad, A.; Bicchi, A.; Buttazzo, G.C. |
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Lecture Notes in Computer Science |
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Series Volume |
4416 |
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yes |
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Call Number |
Sapienza @ mari @ MarTro07 |
Serial |
92 |
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Author |
Mari, Federico; Melatti, Igor; Salvo, Ivano; Tronci, Enrico; Alvisi, Lorenzo; Clement, Allen; Li, Harry |
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Title |
Model Checking Nash Equilibria in MAD Distributed Systems |
Type |
Conference Article |
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Year |
2008 |
Publication |
FMCAD '08: Proceedings of the 2008 International Conference on Formal Methods in Computer-Aided Design |
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1-8 |
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Keywords |
Model Checking, MAD Distributed System, Nash Equilibrium |
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We present a symbolic model checking algorithm for verification of Nash equilibria in finite state mechanisms modeling Multiple Administrative Domains (MAD) distributed systems. Given a finite state mechanism, a proposed protocol for each agent and an indifference threshold for rewards, our model checker returns PASS if the proposed protocol is a Nash equilibrium (up to the given indifference threshold) for the given mechanism, FAIL otherwise. We implemented our model checking algorithm inside the NuSMV model checker and present experimental results showing its effectiveness for moderate size mechanisms. For example, we can handle mechanisms which corresponding normal form games would have more than $10^20$ entries. To the best of our knowledge, no model checking algorithm for verification of mechanism Nash equilibria has been previously published. |
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IEEE Press |
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Piscataway, NJ, USA |
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Cimatti, A.; Jones, R. |
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978-1-4244-2735-2 |
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yes |
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Call Number |
Sapienza @ mari @ MarMelSalTroAlvCle08 |
Serial |
93 |
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Author |
Chierichetti, Flavio; Lattanzi, Silvio; Mari, Federico; Panconesi, Alessandro |
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Title |
On Placing Skips Optimally in Expectation |
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Conference Article |
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2008 |
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Web Search and Web Data Mining (WSDM 2008) |
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15-24 |
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Keywords |
Information Retrieval |
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We study the problem of optimal skip placement in an inverted list. Assuming the query distribution to be known in advance, we formally prove that an optimal skip placement can be computed quite efficiently. Our best algorithm runs in time O(n log n), n being the length of the list. The placement is optimal in the sense that it minimizes the expected time to process a query. Our theoretical results are matched by experiments with a real corpus, showing that substantial savings can be obtained with respect to the tra- ditional skip placement strategy, that of placing consecutive skips, each spanning sqrt(n) many locations. |
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Acm |
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Najork, M.; Broder, A.Z.; Chakrabarti, S. |
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yes |
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Call Number |
Sapienza @ mari @ ChiLatMar08 |
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94 |
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Author |
Mazzini, Silvia; Puri, Stefano; Mari, Federico; Melatti, Igor; Tronci, Enrico |
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Title |
Formal Verification at System Level |
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Conference Article |
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2009 |
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In: DAta Systems In Aerospace (DASIA), Org. EuroSpace, Canadian Space Agency, CNES, ESA, EUMETSAT. Instanbul, Turkey, EuroSpace |
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System Level Analysis calls for a language comprehensible to experts with different background and yet precise enough to support meaningful analyses. SysML is emerging as an effective balance between such conflicting goals. In this paper we outline some the results obtained as for SysML based system level functional formal verification by an ESA/ESTEC study, with a collaboration among INTECS and La Sapienza University of Roma. The study focuses on SysML based system level functional requirements techniques. |
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yes |
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Sapienza @ mari @ Dasia09 |
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20 |
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Author |
Mari, Federico; Melatti, Igor; Salvo, Ivano; Tronci, Enrico; Alvisi, Lorenzo; Clement, Allen; Li, Harry |
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Title |
Model Checking Coalition Nash Equilibria in MAD Distributed Systems |
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Conference Article |
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2009 |
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Stabilization, Safety, and Security of Distributed Systems, 11th International Symposium, SSS 2009, Lyon, France, November 3-6, 2009. Proceedings |
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531-546 |
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We present two OBDD based model checking algorithms for the verification of Nash equilibria in finite state mechanisms modeling Multiple Administrative Domains (MAD) distributed systems with possibly colluding agents (coalitions) and with possibly faulty or malicious nodes (Byzantine agents). Given a finite state mechanism, a proposed protocol for each agent and the maximum sizes f for Byzantine agents and q for agents collusions, our model checkers return Pass if the proposed protocol is an ε-f-q-Nash equilibrium, i.e. no coalition of size up to q may have an interest greater than ε in deviating from the proposed protocol when up to f Byzantine agents are present, Fail otherwise. We implemented our model checking algorithms within the NuSMV model checker: the first one explicitly checks equilibria for each coalition, while the second represents symbolically all coalitions. We present experimental results showing their effectiveness for moderate size mechanisms. For example, we can verify coalition Nash equilibria for mechanisms which corresponding normal form games would have more than $5 \times 10^21$ entries. Moreover, we compare the two approaches, and the explicit algorithm turns out to outperform the symbolic one. To the best of our knowledge, no model checking algorithm for verification of Nash equilibria of mechanisms with coalitions has been previously published. |
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Springer |
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Guerraoui, R.; Petit, F. |
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Lecture Notes in Computer Science |
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5873 |
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yes |
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Sapienza @ mari @ sss09 |
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19 |
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Bobbio, Andrea; Ciancamerla, Ester; Di Blasi, Saverio; Iacomini, Alessandro; Mari, Federico; Melatti, Igor; Minichino, Michele; Scarlatti, Alessandro; Tronci, Enrico; Terruggia, Roberta; Zendri, Emilio |
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Risk analysis via heterogeneous models of SCADA interconnecting Power Grids and Telco networks |
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2009 |
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Proceedings of Fourth International Conference on Risks and Security of Internet and Systems (CRiSIS) |
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90-97 |
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The automation of power grids by means of supervisory control and data acquisition (SCADA) systems has led to an improvement of power grid operations and functionalities but also to pervasive cyber interdependencies between power grids and telecommunication networks. Many power grid services are increasingly depending upon the adequate functionality of SCADA system which in turn strictly depends on the adequate functionality of its communication infrastructure. We propose to tackle the SCADA risk analysis by means of different and heterogeneous modeling techniques and software tools. We demonstrate the applicability of our approach through a case study on an actual SCADA system for an electrical power distribution grid. The modeling techniques we discuss aim at providing a probabilistic dependability analysis, followed by a worst case analysis in presence of malicious attacks and a real-time performance evaluation. |
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Fourth International Conference on Risks and Security of Internet and Systems (CRiSIS) |
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yes |
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Call Number |
Sapienza @ mari @ crisis09 |
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17 |
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