October 2005: It was twenty years ago today

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The team originating the Navigators gathered in 1985, leaded by Paulo Veríssimo, at INESC (Tech. Univ. of Lisboa), where they worked for a number of years. Most of the research work has been focussed on robustness of distributed systems, for applications ranging from office to industrial automation, embedded systems, safety-related. Specialized distributed systems architectures, using media redundancy, reliable multicast protocols, object oriented programming interfaces for group support, etc., have been developed, along with the relevant protocols. Some of these complex protocols have been formally specified and verified.

More recently, already at the University of Lisboa Faculty of Sciences since 1996, the Navigators, with other two teams, were co-founders of LaSIGE (http://lasige.di.fc.ul.pt), a research laboratory of the Department of Informatics. The team organised itself around three research lines, one of which would later give birth to a new team, leaded by Luís Rodrigues. Currently, the Navigators divide their efforts by two problems: fault and intrusion tolerance in open distributed systems; and timeliness and adaptation in dependable systems. See the description of the current activities of the Navigators.


Projects are highly structuring activities for any research group. The Navigators team participated in a number of projects, of which a few deserve special mention.

  • DELTA-4 (1986-1991), a seminal European ESPRIT project, whose results in theory and practice of distributed fault tolerance still influence researchers today. The Navigators introduced pioneering concepts on group-based distributed fault tolerance, such as the AMp group communication suite supporting DELTA-4 replication schemes, and produced prototypes (xAMp) that were incorporated in the project's industrial prototypes. They leaded a workpackage on high-performance distributed and fault-tolerant real-time systems (DELTA-4 XPA), which significantly advanced the state of the art in distributed mission-critical fault-tolerant real-time systems, introducing amongst other results, the well-known semi-active replication algorithm.
  • CORTEX (2001-2004, coordinated by U. Lisboa) was another relevant project achieving important results in the field of autonomous and dynamic event-based systems, introducing innovative concepts such as sentient object computing and wormhole-aware architectures, and new programming models for real-time autonomous and safety-related applications. CORTEX recognition took several forms: the innovative real-time programming model was main feature of a IEEE Distributed Systems OnLine journal issue, was featured in IST Results amongst the most successful projects of the European Commission, and the ideas behind CORTEX have influenced research programs in the EU and the USA.
  • MAFTIA (2000-2003) was again a seminal european IST project that made very important contributions in concepts, architectures and algorithms for intrusion tolerance, a concept based on admitting that systems may suffer intrusions which are dealt with automatically, without failure of the security of the system. The influence and importance of MAFTIA can be measured amongst other things by having reached the final of the highly prestigious European Descartes Science Prize. Ideas behind MAFTIA have influenced research programs in the EU and the USA.
  • CaberNET Network of Excellence (1990-2004) was instrumental for community building in the european scene of distributed and dependable systems. Navigators members belonged to the Executive Board, chaired the respective Information Services Committee, and have set up and managed a trans-european information system.

Other Relevant R&D Facts

  • The team has published extensively in international conferences and journals and elements of the team have co-authored several international books.
  • The team took part in a large number of national and international research projects, profusely producing a balanced combination of scientific and technological results.
  • Members of the team have had a regular presence in the organisation and program committees of international conferences, and in the editorial board of journals, in the area of distributed systems, fault and intrusion tolerance, security, and real-time and embedded systems. Some have served in leadership roles in those communities.


The team has taken part on the successful development of a number of advanced technologies, and the transfer of some to third parties:

  • industrial Delta-4 system pilot for the reliable control of an AGV-driven non-stop engine-block assembly cell in the Renault factory in Paris-France, in 1991 (Delta-4 consortium);
  • industrial Delta-4 system pilot for the reliable, secure and non-stop operation of a distributed home-banking facility, for the Crédit Agricole bank, France, in 1991 (Delta-4 consortium);
  • industrial Dinas system pilot for a distributed and scalable two-level industrial quality control system for the electronic assembly facility of Intracom, Athens-Greece, in 1994 (Dinas consortium);
  • experimental large-scale trans-european information service for use of the Esprit Basic research community, based on the combination of AFS and WWW technologies, for reliability/availability, scalability and user friendliness, in 1994 (CaberNet Infrastructure Task Force).
  • several prototypes resulted from the team's scientific work, namely a group communication suite (xAMp), non-stop duplicated Ethernet and Token-bus physical layers (EPL), a clock synchronisation protocol (A Posteriori Agreement), and a large-scale time service (CesiumSpray), a distributed industrial information platform (NavCim), a large-scale reliable computing platform (NavTech); CANely enhanced distributed F/T system architecture; TTCB Trusted Timely Computing Base wormhole.

Industry Relations

Among national and foreign companies with whom the team has been involved in the course of R&D projects, are: EID-Centrel (pt), Marconi (pt), CTT (pt), SMD (pt), Setcom (pt), Globalsis (pt), Siii (pt), Octal (pt), Bull (fr), Ferranti Computers (uk), MARI (uk), Renault (fr), SEMA Group (fr), GEC Ahlstom (fr), Crédit Agricole (fr), Jeumont-Schneider (fr), Intracom (uk), Hyperion (ie), IDS (us), IBM Research (ch), Microsoft Research (uk), Qinetiq (uk), Carmeq-VW (de), Fujitsu-Siemens Computers (de), Telenor (no), WMC B.V. (nl), Cesi Ricerca (it), Atos Origin (es), Engineering Ingegneria Informatica S.p.A (it), HP Laboratories (uk), SAP Research (fr).

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