Cloud computing has many definitions with different views within industry and academia, but everybody agrees on that cloud computing is the way of making possible the dream of unlimited computing power with high availability. However, being a cloud computing provider seems to be reserved to very large companies that can achieve having a huge data center. The rest of the companies and institutions have to play the role of cloud users. We propose an architecture to organize a set of mini-clouds provided by different institutions, in order to provide a larger cloud that appears to its users as a single one. Such architecture requires selfmanaging behaviour in order to deal with the complexity of matching cloud users requests with the computing utility that mini-clouds of institutions can offer.

Wireless sensor networks are designed for a very wide, yet specific, purpose. Their components have processing and power limitations. Due to these limitations, decisions by running complex algorithms with the information collected by sensors must be done in components external to the WSN. This document presents a combination of WSN and p2p networks to ease the development of systems that rely on WSN functionality. As a result, we propose the creation of a programing abstraction that allows developers to concentrate on the functionality of the developing system. We also propose the use of feedback loops as a way to design and develop the components of the abstraction and to define selfmanaging behavior for them. Those components should be also lowly coupled, interchangeable and extensible.

Fault-tolerance and lookup consistency are considered crucial properties for building applications on top of structured overlay networks. Many of these networks use the ring topology for the organization or their peers. The network must handle multiple joins, leaves and failures of peers while keeping the connection between every pair of successor-predecessor correct. This property makes the maintenance of the ring very costly and temporarily impossible to achieve, requiring periodic stabilization for fixing the ring. We introduce the relaxed-ring topology that does not rely on a perfect successorpredecessor relationship and it does not need any periodic maintenance. Leaves and failures are considered as the same type of event providing a fault-tolerant and selforganizing maintenance of the ring. Relaxed-ring's limitations with respect to failure handling are formally identified, providing strong guarantees to develop applications on top of the architecture. Besides permanent failures, the paper analyses temporary failures and false suspicions caused by broken links, which are often ignored.

Ambient Intelligence scenarios can be deployed even when the environment lacks of a underlying network infrastructure. This can be done using distributed ad-hoc networks. Ambient Intelligence applications can be highly variable and networks can have an unanticipated number of members. Inappropriate distributed network topologies can lead to unstable and inefficient communication. We propose PALTA, a decentralized and self-adaptable network topology. We use feedback loops to model its self-adaptable behaviour and we evaluate its performance using different simulations and measurements. PALTA allows the construction of distributed networks using self-management techniques and maintaining a good overall performance on the network communication.

Installing and upgrading software may introduce conflicts and errors into a system. Transactional Rollback allows the system to return back to a previous, stable and known state. However, to perform such a rollback, it is necessary to store a large amount of information including configuration and installation logs, as well as different versions of software packages. Nevertheless, much of this information is common to several users using the same software and performing the same operations. We can reduce the total amount of storage by having a decentralized architecture using a Distributed Hash Table (DHT) to localise shared resources. We propose a lock-free key/value-set protocol to add and remove data from the DHT. The lock-free protocol is not limited to transactional rollback, and it can be used by other applications that also need value-sets as part of their stored data.