Group Orientation: a Paradigm for Mo dern Distributed Systems Paulo Verssimo Lus Ro drigues Werner Vogels
[email protected] [email protected] [email protected] Tech. Univ. of Lisb oa Tech. Univ. of Lisb oa IST - INESC IST - INESC INESC Abstract of consistency, user-friendliness, p erformance and de- p endability. When lo oking at the several classes of distributed Increasing use of distributed systems, with the cor- activities that may take place in a distributed system, responding decentralisation, stimulates the need for the group concept app ears intuitively: when a group structuring activities around groups of participants, of participants co op erate in an activity (e.g. manage- for reasons of consistency, user-friend liness, perfor- ment of a fragmented database, distributed do cument mance and dependability. Although there is a signi - pro cessing or distributed pro cess control), comp ete in cant number of group communication protocolsinthe an activity (e.g. to share a given resource), or execute literature, they arepenetrating too slow ly in operating a replicated activity for p erformance or fault-tolerance systems technology. Two important reasons are: the reasons (e.g. replicated database server, replicated ac- literal interpretation general ly made of the end-to-end tuator). argument, and the lack of a layer mapping end-user needs (management of replication, competition, coop- Group-orientation, as a general rule, do es not imply eration and group membership) into what is general ly group-oriented programming for the end user. That providedbythecommunication layer: agreement and is, group to ols can help the programmer build appli- order properties.