Documentation/Messaging

Use cases

Event Management

Each component/application generates many different types of events. A centralized event manager (Hub and Spoke) can be used to aggregate/dispatch events

• Synchronization: Window/Leveling events in one window should be synchronized across all viewer windows
• Temporal calibration: Different components have different update frequency, a centralized manager can be used to filter UpdateEvents, so the whole system is updating at the same frequency

AMQP model
Source: http://upload.wikimedia.org/wikipedia/en/9/9d/The-amqp-model-for-wikipedia.svg

System Integration

Different system/application have different data format or are running on different physical devices. A event bus can be used for system integration

Implementation

Using Message Bus and Publisher/Subscriber design pattern for system integration

• OpenIGTLink can be used to define the common message schema, and ZeroMQ can be used to handle the transportation layer abstraction
• ZeroMQ is a small and fast implementation of the Advanced Message Queuing Protocol under the LGPL license
  • It supports both synchronous and asynchronous messaging mode
  • It supportsTCP, Multicast/PGM, Inter-process, and inter-thread transportation
  • CMake version of library can be found here http://github.com/PatrickCheng/zeromq2
  • API can be found here http://api.zeromq.org/zmq.html

Message Bus
Source: http://i.msdn.microsoft.com/dynimg/IC97398.gif

Message Bus
Source: http://i.msdn.microsoft.com/dynimg/IC17158.gif