Abstract

SR is a language for programming distributed systems ranging from operating systems to application programs. On the basis of our experience with the initial version, the language has evolved considerably. In this paper we describe the current version of SR and give an overview of its implementation. The main language constructs are still resources and operations. Resources encapsulate processes and variables that they share; operations provide the primary mechanism for process interaction. One way in which SR has changed is that both resources and processes are now created dynamically. Another change is that inheritance is supported. A third change is that the mechanisms for operation invocation-call and send-and operation implementation-proc and in-have been extended and integrated. Consequently, all of local and remote procedure call, rendezvous, dynamic process creation, asynchronous message passing, multicast, and semaphores are supported. We have found this flexibility to be very useful for distributed programming. Moreover, by basing SR on a small number of well-integrated concepts, the language has proved easy to learn and use, and it has a reasonably efficient implementation.

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A T THE BEGINNING of 2009, we designed a new public exhibition that sought to reveal some of the significant ways in which mapping is ingrained into urban life. It demonstrated how maps work and change over time in response to technology, society and economic imperatives, and highlighted visually striking maps of the city of Manchester.The Mapping Manchester exhibition was on display in the historic reading room of the John Rylands Library on Deansgate, Manchester. It showcased the wealth of cartographic material held by the University of Manchester and other institutions in the city, with generous loans of material from Manchester City Library and Archives and Chetham's Library, including rarely seen maps and obscure plans.We did not want the exhibition to be just a treasures from the collection or a boringly linear here's the history of our town or a boosterist celebration of mapping progress from crude/artistic to sophisticated/scientific or art for art's sake. These maps are more than just pretty pictures. They are powerful tools, instrumental in the making of the contemporary Manchester, and can be read as rich stories of urban life.Over 80 different maps, plans, diagrams and photographs of the city -published over the last 250 years -were displayed. These ranged in date from an excerpt from the first large scale survey of the city published by William Green in 1794, to a 2008 statistical map of binge drinking hotspots across Manchester. A wide range of formats and themes were displayed, from network diagrams, building plans and strip maps, to three-dimensional bird's-eye views and digital animated mapping.Stories covered in the exhibition include; the role of mapping in foretelling developments in the road network and public transport, Manchester as the industrial powerhouse and shock city, the social geography of housing through the changing geographies of Hulme, changing moralities in the mapping of disease and drinking and the pleasures of mapping -brought to life by material from one of the world's first theme parks, Belle Vue. And, of more direct relevance to the interests of readers of this journal, we also presented a range of maps and plans relating to the construction of hydraulic infrastructure.Much of the intellectual challenge in producing the exhibition lay in deciding what to include and what to leave out, from a long list of interesting mapping material. Our rough and ready working criteria

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