1. A Pattern for DRE-s: The MultiGraph Model of Computation Gabor Karsai, Csaba Biegl, Akos Ledeczi, Janos Sztipanovits Institute for Software-Integrated Systems Vanderbilt University Nashville, TN 37235, USA

2. The Challenge of DRE-s Embedded in a physical environment How to express the interaction with the environment? Real-time with strict time-domain behavior How to ensure that timing properties are satisfied? Distributed across multiple platforms How to support distribution in a natural way?

3. The Needs of DRE-s A component model based on concurrent objects with ports with precisely defined model of computation Architectural patterns for system composition and component distribution Control flow and data flow Encapsulation of physical interfaces Simple yet precise rules for calculating time-domain behavior Computational modes: Data-driven + Time-driven + Event-driven Dynamic instantiation and reconfiguration of data- flows in an object network

4. MultiGraph Model of Computation Objects: Actor nodes (script, context, and ports) Data nodes (stream and scalar) Control paradigm: Control flow is tightly coupled with data flow Data/event propagation Request propagation Time-driven behavior Synchronization with external events

5. Multigraph Model of Computation Context Script Context Script Actor: Data: Context Script Context Script Context Script Data/Event flow Request flow

6. MultiGraph Model of Computation Context Script Actor Computational Real-time (I/O synchronized) 2 scripts: Start & Finish Timer (periodic or delay) AND/OR control discipline Data Stream vs scalar Multiple readers and writers

7. MultiGraph Model of Computation

8. Implementation Context Script Context Script Context Script Context Script Multigraph Kernel/Middleware Script API Builder API Control API OS Resources (processors/processes/threads/etc)

9. Patterns with MCM Context Script Context Script Simple forward flow T Context Script I/O Context Script IO triggered by timer Start I/O Data Context Script Context Script Data Context Script Processor boundary Distributor proxy

10. Patterns with MCM Context Script Context Script Downsampler T Context Script I/O Context Script IO with timeout Sample Data(blocked) Data Context Script Start I/O T Context Script Delay timer Data Kill Data

11. MCM Reconfiguration Support Builder and control APIs are available to scripts Operations for Block/unblock data nodes Enable/disable actor nodes Connect/disconnect Empty queues Context Script Context Script Context Script

12. Summary MCM is an architectural pattern that offers coordination services in a dataflow-style computing metaphor Suitable for implementing various communication and coordination patterns Apps: Control system integration platform High-performance signal processing