CSE 298 CSE 300 IOA PRESENTATION May 01

CSE 298 CSE 300 IOA PRESENTATION May 01, 1999 CSE. -IOA-1

CSE 298 CSE 300 IOA 2 JAVA Tool Joe Balthazar Jim Byrne Christine Kenney Ainsley Nathaniel Computer Science & Engineering Department The University of Connecticut 191 Auditorium Road, Box U-155 Storrs, CT 06269 -3155 CSE. -IOA-2

CSE 298 CSE 300 Input/Output Automata Process init(v 1) P 1 Channel decide(v 1) send(m(1, 2)) C(1, 2) receive(m(1, 2)) receive(m(2, 1)) C(2, 1) send(m(2, 1)) init(v 2) P 2 decide(v 2) CSE. -IOA-3

CSE 298 CSE 300 Structure of an IOA m Main components of an I/O Automaton(A): q sig(A), a signature q states(A), a set of states q start states q trans(A), a state-transition relation that follows a precondition-effect style Ø input actions - no preconditions and hence, are permanently enabled Ø internal and output actions - have preconditions and effects q optional tasks CSE. -IOA-4

CSE 298 CSE 300 Objectives m Create a tool to convert the general structure of an IOA to Java code q IOA can be used for algorithm correctness proofs q Recognize only a subset of the language Ø Automaton name, states and data types Ø Input, internal, and output actions Ø Preconditions and effects Parses majority of language Convert a single IOA to a single Java class Produce necessary additional Java code to create a executable program with IOA functionality q Code will run on one machine q m m CSE. -IOA-5

CSE 298 CSE 300 Assumptions m Action names, parameters, and state variables are unique m Deal only basic data types q boolean q double q int m Preconditions and effects written as Java Code q May change state variables so long as same names are used q Code copied directly to Java class CSE. -IOA-6

CSE 298 CSE 300 Assumptions m m Internal and output actions have no parameters q Parameters values selected by IOA code in preconditions based on state q A large enough subset of IOA is not yet implemented to do this Changes to IOA code in parser q All keywords have the first letter capitalized ie. Automaton, Transition, etc. q Some symbols were changed to accommodate the keyboard ie. E - There exist. q Java types were used instead of IOA types- this eliminated the need for a symbol table. q Type checking done by the Java Compiler. CSE. -IOA-7

CSE 298 CSE 300 Java Compiler m Compiler Tool for Java Language. q The Java equivalent of Lex and Yacc q Parses grammar to produce Java code m Java. CC uses an input file written in a standard BNF grammar. q Example of simple BNF grammar q <exp> : : = <simp exp> <rel op> <simp exp> q <rel op> : : = < | >= | <= | > CSE. -IOA-8

CSE 298 CSE 300 Compiler Procedure m Get the tokens q The first part of the JCC specification defines the tokens for the language. m Parse the Language q The second part defines the transitions that make up the language. m Generate the code q The compiler output is generated by the insertion of Java code in the transitions. CSE. -IOA-9

CSE 298 CSE 300 IOA Tokens m m IOA Token definitions. q < AUTOMATON: “Automaton” > q < TRANSITION: “Transition” > q < INPUT: “Input” > q < OUTPUT: “Output” > Resulting Java code is too complicated to put here, looks like assembly language. CSE. -IOA-10

CSE 298 CSE 300 IOA grammar to Java. CC grammar m IOA grammar specification translates directly into JCC grammar because of similarity in structures. q states : : = ‘states’ state, + (‘so’ ‘that’ predicate)? Ø void states() : Ø {} Ø{ Ø <STATES> state()(“, ” state())* Ø (<SO> <THAT> predicate())? Ø} CSE. -IOA-11

CSE 298 CSE 300 Translation of Grammar Cont’d m Java. CC grammar with Java code inserted to create the IOA compiler. q states : : = ‘states’ state, + (‘so’ ‘that’ predicate)? Ø Ø Ø Ø Ø void states() : {} { {String l. Tok. Str; } <STATES> l. Tok. Str = state() {pw. Output. println(l. Tok. Str); } (", " l. Tok. Str = state() {pw. Output. println(l. Tok. Str); })* ( <SO> <THAT> predicate())? } CSE. -IOA-12

CSE 298 CSE 300 Java file which implements the Parser m The IOA compiler takes an automaton definition as input and produces an equivalent automaton, written in Java, as output. Ø static final public void states() throws Parse. Exception { Ø String l. Tok. Str; Ø jj_consume_token(STATES); Ø l. Tok. Str = state(); Ø System. out. println(l. Tok. Str); Ø label_12: Ø while (true) { Ø if (jj_2_38(2)) { ; Ø CSE. -IOA-13

CSE 298 CSE 300 Differences in Grammars m JCC does not permit left recursion and hence two transitions have to be modified. q For example, A C | AB is a transition with left-recursion. q The equivalent transition A CB+ does not contain left recursion and can be used in a Java. CC grammar file. Ø subterm : : = subterm (op. Sym subterm)+ Ø | (quantifier | op. Sym)* op. Sym secondary Ø | (quantifier | op. Sym)* quantifier primary Ø | secondary op. Sym* CSE. -IOA-14

CSE 298 CSE 300 Left Recursion Removed Ø String subterms() : Ø {} Ø { Ø subterm() (op. Sym() subterm())* Ø } Ø Ø Ø Ø String subterm() : {} { ( ((quantifier() | op. Sym())* secondary()) | ((quantifier() | op. Sym())* quantifier() primary()) | ( secondary() (op. Sym())*) ) } CSE. -IOA-15

CSE 298 CSE 300 The Fibonacci. Skew IOA m m What does it do? q Produces the Fibonacci sequence q The sequence can be skewed by a certain value from time to time States q ready indicate state of sequence generation q skew value q print. Flag indicates print state q first, second, current holding last three sequence values CSE. -IOA-16

CSE 298 CSE 300 The Fibonacci. Skew IOA m Actions in the IOA q Input action to start or end the sequence q Input action to skew the sequence q Internal action that calculates the next value in the sequence q Output action that prints the next value CSE. -IOA-17

CSE 298 CSE 300 The Fibonacci. Skew IOA calculate set. Ready skew Fibonacci. Skew print Input Action Internal Action Output Action CSE. -IOA-18

CSE 298 CSE 300 IOA States to Private Data m IOA States automaton Fibonacci. Skew states ready: boolean : = false; skew: int : = 0; print. Flag: boolean : = false; first: int : = 1; sec: int : = 0; current: int : = 0; m Private Data in Java Class class Fibonacci. Skew { // Private Data private boolean ready = false; private int skew = 0; private boolean print. Flag = false; private int first = 1; private int sec = 0; private int current = 0; // Public Methods }; CSE. -IOA-19

CSE 298 CSE 300 Input Action to Public Method m IOA Input Action input set. Ready(flag: boolean) eff $ if (ready!=flag) { ready = flag; first = 1; sec = 0; current = 0; } $ m Public Method in Java Class public void set. Ready(boolean flag) { if (ready!=flag) { ready = flag; first = 1; sec = 0; current = 0; } } CSE. -IOA-20

CSE 298 CSE 300 Input Action to Public Method m IOA Input Action input skew(k: int) eff $ if (ready==true) skew = k; else System. out. println(“Cannot skew: No sequence is being generated”); $ m Public Method in Java Class public void skew(int k) { if (ready==true) skew = k; else System. out. println(“Cannot skew: No sequence is being generated”); } CSE. -IOA-21

Internal and Ouput Actions to Public Methods CSE 298 CSE 300 m IOA Internal Action internal calculate() pre $ return (ready); $ eff $ current = first + second + skew; skew = 0; first = sec; sec = current; print. Flag = true; $ m Public Methods in Java Class public boolean Precalculate() { return (ready); } public void calculate() { current = first + second + skew; . . . } CSE. -IOA-22

Internal and Ouput Actions to Public Methods CSE 298 CSE 300 m IOA Output Action output print() pre $ return (print. Flag); $ eff $ System. out. println(“The current value in sequence is “ + current); print. Flag = false; $ m Public Methods in Java Class public boolean Preprint() { return (print. Flag); } public void print() { System. out. println(“The current value in sequence is “ + current); print. Flag = false; } CSE. -IOA-23

CSE 298 CSE 300 IOA Input Parameters m param. Fibonacci. Skew. java q Created by Parameter. java q Simulates input parameter values for input actions coming in from environment m IOA Input Action parameter input set. Ready(flag: boolean) m Public Java method for each parameter public boolean returnflag() { input = get. Input(“flag”); return retboolean(input); } CSE. -IOA-24

CSE 298 CSE 300 Helper Methods m Methods for converting String to type value private boolean retboolean(String s) { return Boolean. value. Of(s). boolean. Value(); } m Method to get any parameter value from user public String get. Input(String message) { String response = “”; System. out. println(“Enter “ + message); try { Buffered. Reader br. Inp. read. Line(); response = br. Inp. read. Line(); } catch(Exception e){ e. print. Stack. Trace(); } return response; } CSE. -IOA-25

CSE 298 CSE 300 IOA Scheduler m Fibonacci. Skew. Scheduler. java q Created by Scheduler. java q Contains main program which calls a round robin scheduler to cycle through actions public static void Round. Robin() { boolean Not. Quit; Fibonacci. Skew ioa. Fibonacci. Skew = new Fibonacci. Skew(); param. Fibonacci. Skew input. Fibonacci. Skew = new param. Fibonacci. Skew(); while(Not. Quit) { // Check each action Not. Quit = askuser(“cycle again”); } } CSE. -IOA-26

CSE 298 CSE 300 Round Robin Scheduler while(Not. Quit) { if(askuser(“set. Ready”)) { ioa. Fibonacci. Skew. set. Ready( input. Fibonacci. Skew. Returnflag()); } if(askuser(“skew”)) { ioa. Fibonacci. Skew. skew( input. Fibonacci. Skew. Returnk()); } if(ioa. Fibonacci. Skew. Pre. Calculate()) { ioa. Fibonacci. Skew. calculate(); } if(ioa. Fibonacci. Skew. Preprint()) { ioa. Fibonacci. Skew. print(); } Not. Quit = askuser(“cycle again”); } Input Internal Output CSE. -IOA-27

CSE 298 CSE 300 Future Research m Solving Composition of Automata q Public Composed IOA Class Approach Ø All classes are in a package Ø Each independent IOA class is private Ø The composed IOA class is public q IOA Class Library Approach Ø All IOAs have their own class in a library Ø Create a new composed IOA importing 2 or more IOA classes from the library Ø Put back composed classes in library and reuse q Combination of Both Ø Package last composition of classes from library q Adapt parser to handle assumes clause CSE. -IOA-28

CSE 298 CSE 300 Future Research m m m Generation of pre-conditions and effects in Java Determining parameters for internal and output actions q Common mechanism for selecting values from state Consider distributed systems modeled by IOA q Interaction in Java q Use of Java distributed technologies CSE. -IOA-29

CSE 298 CSE 300 References m m m MIT-Theory of Distributed Systems Group q I/O Automata Model, Language and Tool Set. http: //theory. lcs. mit. edu/tds/~vaziri/ioa. html q S. J. Garland, N. A. Lynch, and M. Vaziri, “IOA: A Language for Specifying, Programming, and Validating Distributed Systems Draft”, December 1997. O. M. Cheiner and A. A. Shvartsman, “Implementing An Eventually-Serializable Data Service as a Distributed System Building Block”, July 1998. Java Compiler - The Java Parser Generator - http: //www. suntest. com/Java. CC/ CSE. -IOA-30

CSE 298 CSE 300 Flow IOA. jj grammar file javacc IOA. java associated Java files ioaname. ioa javac Method. Info. java Scheduler. java Parameter. java *. class java Executable IOA ioaname. java ioaname. Scheduler. java paramioaname. java ioaname. Scheduler java *. class javac CSE. -IOA-31