CSCW infrastructure

1
CSCW infrastructure

• Ian MacColl
• ianm_at_dcs.gla.ac.uk
• http//www.dcs.gla.ac.uk/ianm/hci4/
• Background
• Middleware
• Elvin
• EQUIP

2
Background problems

• Concurrent distributed processes
• Creation, interconnection, communication
• Performance and latency
• Synchronisation and exclusion
• Complexity
• And then there are the people

3
Background abstractions

• Abstractions
• Coordinating threads/processes
• Updating common model
• Controlling views derived from model
• Implementations
• Multicast RPC
• Events and notifiers
• Shared model and views

4
Middleware

• Distributed system services

Application
Application
MIDDLEWARE
Platform
Platform
5
Middleware types

• Transaction processing
• Remote procedure call (RPC)
• Object request brokers (ORBs)
• Message-oriented middleware (MOM)

6
Middleware MOM

• Compare RPC/RMI
• Asynch peer-to-peer data exchange
• Message recipients interpret and act
• Typically queued and event-based

7
elvin

• DSTC, Australia
• Disposable interaction
• Loose content-based notification
• Routes undirected dynamically typed messages from
  producers to consumers
• http//elvin.dstc.edu.au

8
elvin content-based routing

• Compare channel-based routing
• Producers push messages to server
• Messages are name-value pairs
• Consumers request message classes
• Subscription language for requests
• Advanced quench correlate federate

9
elvin techniques

• Multi-language C Java Python Perl
• Ordered at most once delivery
• Extremely efficient matching
• Variety of transports

10
EQUIP

• EQUATOR, UK
• Ubiquitous computing (UBICOMP)
• Lightweight infrastructure enabling devices to
  share information
• Physical and digital state
• Combines tuple-spaces and CVEs
• http//www.equator.ac.uk

11
EQUIP tuple spaces

• Examples Linda JavaSpaces Tspaces
• Space is persistent shared memory
• Template-based matching
• Operations write read take notify
• Advanced transactions, leases

12
EQUIP CVEs

• Examples Dive Massive quake?
• Real-time 3D graphics and audio environments for
  collaboration
• Immersive or non-immersive
• Substantial network, graphics, concurrency and
  interaction issues

13
EQUIP techniques

• Multi-language C Java
• Uses NSPR Bamboo VRJuggler IDL
• Multiple independent spaces
• Asynchronous communication
• Flexible discovery
• Persistent event-based matching
• Explicit update

14
EQUIP shared data service

• Indirect inter-process communication
• Components
• Dataspaces
• Items add update delete
• Patterns add remove

15
Conclusion

• CSCW infrastructure
• Concurrent distributed systems
• Middleware
• Distributed systems services
• elvin
• Disposable interaction
• Content-based notification
• EQUIP
• Ubiquitous computing
• Space-based state sharing

16
References

• Bernstein, Middleware A model for distributed
  system services, CACM 39.286-98
• Fitzpatrick et al, Augmenting the workaday world
  with Elvin, ECSCW99 431-451
• Greenhhalgh et al, The EQUIP platform Bringing
  together physical and virtual worlds, working
  draft

17
ElvinProducer.java

• // connect to the "test" scope
• Producer prod new Producer("test")
  
• for (int i 0 i lt 10 i)
• // create a notification
• Notification notif new
  Notification()
• notif.put("demo","hello")
• notif.put("count", i 1)
• // send the notification
• prod.notify(notif)
• System.out.println("sent "notif)
• Thread.sleep(1000)

18
ElvinConsumer.java

• // connect to the "test" scope
• Consumer cons new Consumer("test")
• // create a subscription
• Subscription sub new Subscription("requi
  re(demo)")
• // register a listener
• sub.addNotificationListener(new
  ElvinConsumer())
• // activate the subscription
• cons.addSubscription(sub)
• System.out.println("waiting...")