In the last few years, the increasing use of the Internet and geo-political, sociological and financial changes induced by globalization, are paving the way for a connected world where the information is always available at the right place and the right time. As such, applications previously deployed for ``closed'' environmets, are now federating into geographically distributed systems connected through a Wide Area Network (WAN). By this evolution, in the near future no system will be isolated: every system will be composed by interconnected systems, i.e., it will be a System of Systems (SoS). Example of SoS are the Large-scale Complex Critical Infrastructure (LCCIs), such as power grids, transport infrastructures (airports and seaports), financial infrastructures, next generation intelligence platforms, to cite a few. In these systems, multiple sources of information generate a high volume of events that need to be delivered to all intended destinations by respecting several Quality of Service (QoS) constraints imposed by the critical nature of LCCIs. As such, particular attention is devoted to the middleware solution used to disseminate information in the SoS. Due to its inherently scalability provided by space, time and synchronization decoupling properties, the publish/subscribe paradigm is becoming attractive for the implementation of a middleware service for LCCIs. However, scalability is not the only requirement exhibited by SoS. Several services need to control a broader set of QoS requirements, such as timeliness, ordering and reliability. Unfortunately, current middleware solutions do not address QoS constraints required by SoS. Current publish/subscribe middleware solutions for the WAN environment offer only a best effort event dissemination, with no additional control on QoS. Just a few implementations try to address some isolated QoS policy, making them not suitable for a SoS scenario. The contribution of this thesis is to devise a QoS layer that can be posed on top of a generic publish/subscribe middleware that enriches its service by addressing: (i) ordering, (ii) reliability and (iii) timeliness in event dissemination in SoS over WAN. Specifically, we first analyze several real case studies, by highlighting their QoS requirements in terms of ordering, reliability and timeliness, and compare these requirements with both current research prototypes and commercial systems. Then, we fill the gap by proposing novel algorithms to address those requirements. The proposed protocols can also be combined together in order to provide the QoS level required by the particular application. In this way, QoS issues do not need to be addressed at application level, so as to leave applications to implement just their native functionalities
