Modeling and Visualization of CFSM Networks in JavaTime Michael Shilman James Shin Young EE249 Project Presentation December 8, 1998

Outline Introduction JavaTime Components Abstract Reactive Model Modeling of CFSM’s AR and CFSM JavaTime Packages Visualization of CFSM Networks Design Example - Seatbelt Controller Conclusions

Introduction The JavaTime Project –Collection of tools, libraries, and methodologies for embedded systems design. –Use Java TM, enhanced via packages, as textual design input syntax. –Graphical input syntax and visualization infrastructure. –Common model for system representation Goals for EE249 –Incorporate CFSM model into JavaTime environment. –Describe, visualize, and execute CFSM networks on standard Java platforms.

JavaTime Component Package Components –Central design entities. Ports –Access points for connecting components. Connections –Relation between ports. Containers –Hierarchical nesting of components and containers

The Abstract Reactive Model Components react to all input events. Events are changes in signal values. Fully asynchronous communication. –No events happen “at the same time.” Networks for abstraction –Temporal and structural abstraction –Fundamental-mode asynchronous assumption. –All internal signals converge to a stable value before output is emitted. Used in JavaTime as building block for describing other models.

The javatime.jcp.ar Package ARComponent –User specifies behavior by defining the react(ARPort p, Object v) method. ARNetwork –Executes components contained within according to semantics of AR model. ARThread –Enables Esterel-style description of component behavior. public class Foo extends ARComponent { public void react() { // do something }

Modeling CFSM’s in AR CFSM’s are modeled as AR components with two implicit ports. –Activate input, runnable output Transitions of CFSM’s controlled by scheduler component.

The javatime.jcp.cfsm Package Implemented using the javatime.jcp.ar package. CFSM –User specifies behavior by defining transition() method. –eventPresent(Input I) method tests for presence of events. CFSMNet –Contains a scheduler component responsible for activating CFSM’s. CFSMThread –Esterel-style input for CFSM’s. public class Bar extends CFSM { public void transition() { // do something }

Esterel-style Programs in Java Esterel provides compact syntax for synchronous reactive programming. –await, do watching, ||, etc. Construct similar conveniences in Java. –Provided in ARThread, CFSMThread classes. –await, awaitWatching, methods. –Uses standard Java threads, monitors to implement Esterel-like facilities. –Maintains compatibility with standard Java syntax, tools, and execution platforms. public class Blah extends ARThread { public void run() { while(true) { // do something await(); }

CFSM Visualization Focus on infrastructure rather than application –Make it easy to construct visualizations, rather than trying to pre-package all possible visualizations. –Able to develop in parallel with modeling effort. Our goal: view, edit, and animate component networks at different levels of abstraction

Visualization Probes Components which sample signals to construct visualizations. –Modular and easy to write; drag and drop just like any other component. –Probe to modify network display as system executes, via protocol-based API. Image probes at different stages in a JPEG decoder

Animation and Instrumentation Listener interface allows monitoring of execution state. Instrumentation by procedural insertion of probes. –Simple traversal of JCP design hierarchy. Code instrumentation using JavaTime AST tools. –Create extra output ports to communicate instrumentation results.

Visualization Protocols Software protocols for reusable visualization surfaces. –Support for incremental update. –Read/modification capabilities. Sample protocols:

Anatomy of a Protocol Filters: - scheduler, activate/runnable ports - visualization probes Filters: - scheduler, activate/runnable ports - visualization probes Multiple views: - standard - sketch -... Multiple views: - standard - sketch -...

Multi-Syntax Editing Different visual syntax for different models of computation. –Illustrate relationship between different models. CFSM ViewAR View

Design Example Implemented the POLIS seatbelt controller example using javatime.jcp.cfsm package. Original design –CFSM behavior described with two Esterel modules. –CFSM network described in Ptolemy. Ported design –CFSM’s described as Java classes. –Network also a Java class.

Design Example - Esterel module belt_control: input reset, key_on, key_off, belt_on, end_5, end_10; output alarm(boolean), start_timer; loop do emit alarm(false); every key_on do do emit start_timer; await end_5; emit alarm(true); await end_10; watching [key_off or belt_on]; emit alarm(false); end watching reset end.

Design Example - JavaTime public void run() { Condition watch = new Condition() { public boolean isTrue() { return (eventPresent(_reset) || eventPresent(_keyOff) || eventPresent(_beltOn)); } }; while (true) { try { emit(_alarm,Boolean.FALSE); awaitWatching(_reset); if (eventPresent(_keyOn)) { try { emit(_startTimer); awaitWatching(_end5, watch); emit(_alarm,Boolean.TRUE); awaitWatching(_end10, watch); } catch (WatchException e) { if (eventPresent(_reset)) { throw e; } emit(_alarm,Boolean.FALSE); } } catch (WatchException e) {} }

Conclusions Java as an input syntax for reactive systems. –Resulting specification not as concise as Esterel... –…but provides compatibility with standard Java tools. Programming language “extensions” as packages. –Extends utility of a language without compromising compatibility. –Avoid high overhead of new language development; a good option for niche domains. Relationship between AR and CFSM models. –CFSM networks can be modeled as AR systems. –The reverse is probably also true.

More Conclusions Visual editing and animation of systems –Multi-syntax editing reveals relationship between models of computation. –Software protocols enable rapid development of interactive visualizations. –Visualization probes simplify user-level construction of visualizations.