Ptolemy Project Vision

Edward A. LeeRobert S. Pepper Distinguished Professor

Eighth Biennial Ptolemy Miniconference

April 16, 2009Berkeley, CA, USA

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Cyber-Physical Systems (CPS)Where it is going

CPS: Orchestrating networked computational resources with physical systems.

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Cyber Physical Systems:Computational +

Physical

CPS is Multidisciplinary

Computer Science:

Carefully abstracts the physical world

System Theory:

Deals directly with physical quantities

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Ptolemy Project Research

Foundations: Timed computational semantics.

Bottom up: Embedded processors (PRET).

Top down: Distributed real-time systems (PTIDES).

Holistic: Scalable model-based design.

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Object Oriented vs. Actor OrientedSoftware Components

The alternative: Actor oriented:

actor name

data (state)

ports

Input data

parameters

Output data

What flows through an object is

evolving data

class name

data

methods

call return

What flows through an object is

sequential control

The established: Object-oriented:

Things happen to objects

Actors make things happen

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Timed Software Semantics

s S N

Causal systems operating on signals are usually naturally (Scott) continuous.

concurrent actor-oriented models

abstraction

fixed-point semantics

super-dense time

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Results

Papers:[1] Lee and Matsikoudis, "

The Semantics of Dataflow with Firing," in From Semantics to Computer Science: Essays in memory of Gilles Kahn, Cambridge 2009.

[2] Ye Zhou and Edward A. Lee. "Causality Interfaces for Actor Networks," ACM Trans. on Embedded Computing Systems, April 2008.

[3] Liu and Lee, "CPO Semantics of Timed Interactive Actor Networks,” Theoretical Computer Science 409 (1): pp.110-25, 2008..

[4] Lee, " Application of Partial Orders to Timed Concurrent Systems," article in Partial order techniques for the analysis and synthesis of hybrid and embedded systems, in CDC 07.

[5] Lee and Zheng, "Leveraging Synchronous Language Principles for Heterogeneous Modeling and Design of Embedded Systems," EMSOFT ’07.

[6] Liu, Matsikoudis, and Lee. "Modeling Timed Concurrent Systems," CONCUR ’06.

[7] Cataldo, Lee, Liu, Matsikoudis and Zheng "A Constructive Fixed-Point Theorem and the Feedback Semantics of Timed Systems," WODES'06

etc. ...

Software:Ptolemy II realizes a number of

timed concurrent models of computation (MoCs) with well-founded rigorous semantics.

Ph.D. Theses:

[1] Haiyang Zheng, "Operational Semantics of Hybrid Systems," May 18, 2007.

[2] Ye Zhou, "Interface Theories for Causality Analysis in Actor Networks," May 15, 2007.

[3] Xiaojun Liu, "Semantic Foundation of the Tagged Signal Model," December 20, 2005.

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Ptolemy II: Our Laboratory for Actor-Oriented Models of Computation

Director from an extensible library defines component interaction semantics or “model of computation.”

Extensile, behaviorally-polymorphic component library.

Visual editor supporting an abstract syntax

Type system for transported data

Concurrency management supporting dynamic model structure.

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Ptolemy Project Research

Foundations: Timed computational semantics.

Bottom up: Embedded processors (PRET).

Top down: Distributed real-time systems (PTIDES).

Holistic: Scalable model-based design.

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Bottom Up: Embedded Processors

Precision-Timed (PRET) MachinesMake temporal behavior as important as logical function.

Timing precision with performance: Challenges: Memory hierarchy (scratchpads?) Deep pipelines (interleaving?) ISAs with timing (deadline instructions?) Multicore (dedicated I/O & real-time processors?) Predictable memory management (Metronome?) Languages with timing (discrete events? Giotto?) Predictable concurrency (synchronous languages?) Composable timed components (actor-oriented?) Precision networks (TTA? Time synchronization?)

See S. Edwards and E. A. Lee, "The Case for the Precision Timed (PRET) Machine," in the Wild and Crazy Ideas Track of the Design Automation Conference (DAC), June 2007.

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PRET Project (Berkeley, Columbia)

Funding from NSF, Toyota, National Instruments, plus cooperation with Xilinx, Synfora, and Tidorum

Staffing: Edward A. Lee (UCB PI) Stephen Edwards (Columbia co-PI) Jan Rabaey (UCB co-PI) John Wawrzynek (UCB co-PI) Christopher Brooks (Technical staff) Hiren Patel (postdoc) Hugo Andrade (NI VIF) Shanna-Shaye Forbes (UCB grad student) Sunjun Kim (Columbia grad student) Ben Lickly (UCB grad student) Isaac Liu (UCB grad student)

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Ptolemy Project Research

Foundations: Timed computational semantics.

Bottom up: Embedded processors (PRET).

Top down: Distributed real-time systems (PTIDES).

Holistic: Scalable model-based design.

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PTIDES: Programming Temporally Integrated Distributed Embedded Systems

Distributed execution under DE semantics, with “model time” and “real time” bound at sensors and actuators.

Input time stamps are ≥ real time

Input time stamps are ≥ real time

Output time stamps are ≤ real time

Output time stamps are ≤ real time

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PTIDES Project

Funding from NSF, Agilent, IBM, Toyota, and the State of California MICRO program, in cooperation with the University of Salzburg, Austria.

Staffing: Edward A. Lee (UCB PI) Christopher Brooks (Technical staff) Patricia Derler (Univ. Salzburg grad student) Slobodan Matic (postdoc) Thomas Feng (UCB grad student) Ben Lickly (UCB grad student) Stefan Resmerita (Univ. Salzburg technical staff) Yang Zhao (UCB grad student, Google technical staff) Jia Zou (UCB grad student)

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Ptolemy Project Research

Foundations: Timed computational semantics.

Bottom up: Embedded processors (PRET).

Top down: Distributed real-time systems (PTIDES).

Holistic: Scalable model-based design.

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Hierarchical MultimodelingHierarchical compositionsof models of computation. Maintaining temporal semantics across MoCs is a main challenge.

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Multi-View Modeling:Distinct and separate models of the same system are constructed to model different aspects of the system.

Functional model in Statecharts

Functional model in Ptolemy II

Deployment model in Ptolemy II

Verification model in SMV

Reliability model in Excel

This example is a test case for a collaborative project with Lockheed-Martin

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“Model Engineering” Project

Funding from AFRL, Army Research Office, Air Force Research Office, Bosch, Lockheed-Martin, and Thales.

Staffing: Edward A. Lee (UCB PI) Christopher Brooks (Technical staff) Chihong (Partrick) Cheng (TU Munich) Thomas Huining Feng (UCB grad student) Jackie Mankit Leung (UCB grad student) Eleftherios Matisikoudis (UCB grad student) Stavros Tripakis (Visiting Research Scientist)

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Addressing the Design Challenges for Cyber Physical Systems

Foundations: Timed computational semantics. Abstract semantics on super-dense time

Bottom up: Make timing repeatable. Precision-timed (PRET) machines

Top down: Timed, concurrent components. Distributed real-time discrete-events (PTIDES)

Holistic: Model engineering. Mulimodeling, ontologies, property system, …