The widespread adoption of Free and Open Source Software (FOSS) in many strategic contexts of the information technology society has drawn the attention on the issues regarding how to handle the complexity of assembling and managing a huge number of (packaged) components in a consistent and effective way. FOSS distributions (and in particular GNU/Linux-based ones) have always provided tools for managing the tasks of installing, removing and upgrading the (packaged) components they were made of. While these tools provide a (not always effective) way to handle these tasks on the client side, there is still a lack of tools that could help the distribution editors to maintain, on the server side, large and high-quality distributions. In this paper we present our research whose main goal is to fill this gap: we show our approach, the tools we have developed and their application with experimental results. Our contribution provides an effective and automatic way to support distribution editors in handling those issues that were, until now, mostly addressed using ad-hoc tools and manual techniques.

C FT is a new co nstraint system providing reco rds as logi cal dat.a st ru cture fo r co nstraint (logi c) programming. It can be seen as a genera lizat io n of th e rational tree system employed in Prolog If, where fin er-g rained constr a ints are used , and where subtrees are id entifi ed by key words rath er than by position. C FT is defined by a first-ord er structure consisting of so-called feature trees. Feature trees generali ze th e ordinary trees co rres ponding to first-ord er terms by hav ing th eir edges labeled with fi eld nam es call ed feat ures. The m at hem at ical semanti cs given by the feature trer st ru cture is com plemented with a log ical se m a nt ics given by five axiolll schemes, wh ich we co nj ect ure to co mprise a co mpl ete axiomatization of th e feat ure tree structure. We present a decision m et hod for CFT, wh ich dec id es entailm ent a nd disentailment betwee n possibly existentially quant.ifi ed constraints. Since C FT satisfies th e independ ence property, our dec ision m ethod can a lso be employed for checking the satisfiability of co njunctions of positive a nd negat ive constraints. This includ es quantifi ed negative co nstraints such as VyVz(x 1: f(y , z)). Th e paper also presents an id ealized abstract machin e process ing negat ive a nd positive co nstra ints in crem entally. We argue that an optimized version of the m achin e can decid e satisfiabi li ty and e ntailm ent in quasi-lillear time.

Abstract. Cryptographic protocols are small programs which involve a high level of concurrency and which are difficult to analyze by hand. The most successful methods to verify such protocols rely on rewriting techniques and automated deduction in order to implement or mimic the process calculus describing the protocol execution. We focus on the intruder deduction problem, that is the vulnerability to passive attacks, in presence of several variants of AC -like axioms (from AC to Abelian groups, including the theory of exclusive or ) and homomorphism which are the most frequent axioms arising in cryptographic protocols. Solutions are known for the cases of exclusive or, of Abelian groups, and of homomorphism alone. In this paper we address the combination of these AC -like theories with the law of homomorphism which leads to much more complex decision problems. We prove decidability of the intruder deduction problem in all cases considered. Our decision procedure is in EXPTIME, except for a restricted case in which we have been able to get a PTIME decision procedure using a property of one-counter and pushdown automata.

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Complex networked applications are assembled by connecting software components distributed across multiple machines. Building and deploying such systems is a challenging problem which requires a significant amount of expertise: the system architect must ensure that all component dependencies are satisfied, avoid conflicting components, and add the right amount of component replicas to account for quality of service and fault-tolerance. In a cloud environment, one also needs to minimize the virtual resources provisioned upfront, to reduce the cost of operation. Once the full architecture is designed, it is necessary to correctly orchestrate the deployment phase, to ensure all components are started and connected in the right order.We present a toolchain that automates the assembly and deployment of such complex distributed applications. Given as input a high-level specification of the desired system, the set of available components together with their requirements, and the maximal amount of virtual resources to be committed, it synthesizes the full architecture of the system, placing components in an optimal manner using the minimal number of available machines, and automatically deploys the complete system in a cloud environment.

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Determining whether two or more packages cannot be installed together is an important issue in the quality assurance process of package-based distributions. Unfortunately, the sheer number of different configurations to test makes this task particularly challenging, and hundreds of such incompatibilities go undetected by the normal testing and distribution process until they are later reported by a user as bugs that we call "conflict defects". We performed an extensive case study of conflict defects extracted from the bug tracking systems of Debian and Red Hat. According to our results, conflict defects can be grouped into five main categories. We show that with more detailed package meta-data, about 30 % of all conflict defects could be prevented relatively easily, while another 30 % could be found by targeted testing of packages that share common resources or characteristics. These results allow us to make precise suggestions on how to prevent and detect conflict defects in the future.

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