Robust inference of trees

This paper is concerned with the reliable inference of optimal tree-approximations to the dependency structure of an unknown distribution generating data. The traditional approach to the problem measures the dependency strength between random variables by the index called mutual information. In this paper reliability is achieved by Walley's imprecise Dirichlet model, which generalizes Bayesian learning with Dirichlet priors. Adopting the imprecise Dirichlet model results in posterior interval expectation for mutual information, and in a set of plausible trees consistent with the data. Reliable inference about the actual tree is achieved by focusing on the substructure common to all the plausible trees. We develop an exact algorithm that infers the substructure in time O(m ⁴), m being the number of random variables. The new algorithm is applied to a set of data sampled from a known distribution. The method is shown to reliably infer edges of the actual tree even when the data are very scarce, unlike the traditional approach. Finally, we provide lower and upper credibility limits for mutual information under the imprecise Dirichlet model. These enable the previous developments to be extended to a full inferential method for trees.     

Unraveling robustness of deep face anti-spoofing models against pixel attacks

Multimedia Tools and Applications - In the last few decades, deep-learning-based face verification and recognition systems have had enormous success in solving complex security problems. However,...     

Consumers' Creative Talent: Which Characteristics Qualify Consumers for Open Innovation Projects? An Exploration of Asymmetrical Effects

Virtual customer integration and open innovation are considered as appropriate means to improve the success of new product development. However, only when consumers are qualified and motivated to contribute promising ideas and relevant know‐how they are able to add value to a producer's innovation process. In this study, we explore the symmetric and asymmetric impact of various creativity components on consumers' idea generation, concept development, or prototype building abilities as well as interest in co‐creation projects. Our results show that creativity components are of different importance. While some characteristics are needed above certain thresholds to successfully accomplish a certain development task, exceeding those does not necessarily lead to better outputs. Other characteristics improve the creative output only if they exceed specific levels.     

A Method for Patching Interleaving-Replay Attacks in Faulty Security Protocols

The verification of security protocols has attracted a lot of interest in the formal methods community, yielding two main verification approaches: i) state exploration, e.g. FDR [Gavin Lowe. Breaking and fixing the needham-schroeder public-key protocol using FDR. In TACAs'96: Proceedings of the Second International Workshop on Tools and Algorithms for Construction and Analysis of Systems, pages 147–166, London, UK, 1996. Springer-Verlag] and OFMC [A.D. Basin, S. Mödersheim, and L. Viganò. An on-the-fly model-checker for security protocol analysis. In D. Gollmann and E. Snekkenes, editors, ESORICS'03: 8th European Symposium on Research in Computer Security, number 2808 in Lecture Notes in Computer Science, pages 253–270, Gjøvik, Norway, 2003. Springer-Verlag]; and ii) theorem proving, e.g. the Isabelle inductive method [Lawrence C. Paulson. The inductive approach to verifying cryptographic protocols. Journal in Computer Security, 6(1-2):85–128, 1998] and Coral [G. Steel, A. Bundy, and M. Maidl. Attacking the asokan-ginzboorg protocol for key distribution in an ad-hoc bluetooth network using coral. In H. König, M. Heiner, and A. Wolisz, editors, IFIP TC6 /WG 6.1: Proceedings of 23rd IFIP International Conference on Formal Techniques for Networked and Distributed Systems, volume 2767, pages 1–10, Berlin, Germany, 2003. FORTE 2003 (work in progress papers)]. Complementing formal methods, Abadi and Needham's principles aim to guide the design of security protocols in order to make them simple and, hopefully, correct [M. Abadi and R. Needham. Prudent engineering practice for cryptographic protocols. IEEE Transactions on Software Engineering, 22(1):6–15, 1996]. We are interested in a problem related to verification but far less explored: the correction of faulty security protocols. Experience has shown that the analysis of counterexamples or failed proof attempts often holds the key to the completion of proofs and for the correction of a faulty model. In this paper, we introduce a method for patching faulty security protocols that are susceptible to an interleaving-replay attack. Our method makes use of Abadi and Needham's principles for the prudent engineering practice for cryptographic protocols in order to guide the location of the fault in a protocol as well as the proposition of candidate patches. We have run a test on our method with encouraging results. The test set includes 21 faulty security protocols borrowed from the Clark-Jacob library [J. Clark and J. Jacob. A survey of authentication protocol literature: Version 1.0. Technical report, Department of Computer Science, University of York, November 1997. A complete specification of the Clark-Jacob library in CAPSL is available at http://www.cs.sri.com/millen/capsl/].     

Virtual worlds as knowledge management platform – a practice‐perspective

Virtual worlds, as electronic environments where individuals can interact in a realistic manner in form of avatars, are increasingly used by gamers, consumers and employees. Therefore, they provide opportunities for reinventing business processes. Especially, effective knowledge management (KM) requires the use of appropriate information and communication technology (ICT) as well as social interaction. Emerging virtual worlds enable new ways to support knowledge and knowing processes because these virtual environments consider social aspects that are necessary for knowledge creating and knowledge sharing processes. Thus, collaboration in virtual worlds resembles real‐life activities. In this paper, we shed light on the use of Second Life (SL) as a KM platform in a real‐life setting. To explore the potential and current usage of virtual worlds for knowledge and knowing activities, we conducted a qualitative study at IBM. We interviewed IBM employees belonging to a special workgroup called ‘Web 2.0/virtual worlds’ in order to gain experience in generating and exchanging knowledge by virtually collaborating and interacting. Our results show that virtual worlds – if they are able to overcome problems like platform stability, user interface or security issues – bear the potential to serve as a KM platform. They facilitate global and simultaneous interaction, create a common context for collaboration, combine different tools for communication and enhance knowledge and knowing processes.     

Development of an assembly process and reliability investigations for flip-chip LEDs using the AuSn soldering

 A packaging process for flip-chip LEDs (light emitting diodes) is described. The LEDs are picked and placed on a silicon substrate wafer. After reflow the substrates are individualized. AuSn solder is used for the interconnection. The solder compounds, Au and Sn, are electroplated separately: Sn on the silicon substrate and Au on the chip. The interconnections formed by tin-rich and by gold-rich intermetallic phases are compared. The metallurgy and the reliability of the LEDs are investigated. The superiority of the gold-rich interconnection is demonstrated. Received: 30 May 2001 / Accepted: 17 July 2001     

A Pragmatic Approach to Reuse in Tactical Theorem Proving

In interactive theorem proving, tactics and tacticals have been introduced to automate proof search. In this scenario, user interaction traditionally is restricted to the mode in which the user decides which tactic to apply on the top-level, without being able to interact with the tactic once it has begun running.We propose a technique to allow the implementation of derivational analogy in tactical theorem proving. Instead of replaying tactics including backtracked dead ends our framework makes choice points in tactics explicit and thus avoids dead ends when reusing tactics. Additionally users can override choices a tactic has made or add additional steps to a derivation without terminating the tactic. The technique depends on an efficient replay of tactic executions without repeating search that the original computation may have involved.     

Coloring Terms to Control Equational Reasoning

In this article we present an approach to prove the equality between terms in a goal-directed way developed in the field of inductive theorem proving. The two terms to be equated are syntactically split into expressions that are common to both and those that occur only in one term. According to the computed differences we apply appropriate equations to the terms in order to reduce the differences in a goal-directed way. Although this approach was developed for purposes of inductive theorem proving – we use this technique to manipulate the conclusion of an induction step to enable the use of the hypothesis – it is also a powerful method for the control of equational reasoning in general.     

Annotated reasoning

The application of deduction in various domains resulted in a variety of different techniques to guide the proof search. Many of these techniques incorporate additional knowledge to restrict or select possible proof steps. As a consequence, usually the underlying calculus has to be modified to keep track of this information during the proof search. In this paper we present a general framework for maintaining additional strategic knowledge within a proof. We introduce a formal notion of annotations attached to the constituents of formulas and illustrate how a generic method of inheriting these annotations can be instantiated for various purposes. This revised version was published online in June 2006 with corrections to the Cover Date.