tcc, with history radha jagadeesan (with vineet gupta and vijay saraswat)
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TCC, With HistoryRADHA JAGADEESAN
(WITH VINEET GUPTA AND VIJAY SARASWAT)
TCC, With HistoryA SUBJECTIVE TOUR OF ONE LINE OF JOINT RESEARCH WITH PRAKASH.
INGREDIENTS THAT BUILD UP TO THE PAPER IN PROCEEDINGS
PAPER IN PROCEEDINGS IS BETTER REFERENCED THAN THIS TALK
Reminiscing …
Joined Cornell for Ph. D in Fall 1987.
My first research project with Prakash: 1988 Summer
Stone Duality lectures by Prakash and Dexter [Spring 88 , Fall 88, Spring 89??]
Don’t let the perpetually cheerful mien of these two gentlemen fool you!
Id [Arvind, Nikhil, Pingali, ~80s]
“Copy problem” x[3] = …
often results in a copy of array x
Updatable shared memory
Aims to be deterministic:
so, monotone shared memory via
logic variables
x
X[2]=array[5] x[1]=4X[0]=2
Id [Arvind, Nikhil, Pingali, ~80s]
x
X[2]=array[5] x[1]=4X[0]=2
Write write conflicts: solved by unification
Read write conflicts: solved by blocking reads
Id [Arvind, Nikhil, Pingali, ~80s]
xRead write conflicts: solved by blocking reads
x = array(2*n), x[0] =1
for (i=1; i<n; i++) { x[2*i ] = 2*x[2*i-1]
for (i=0; i<n; i++) { x[2*i+1] = 2*x[2*i]
Programs as constraints
xx = array(2*n), x[0] = 1for (i=1; i<n; i++) { x[2*i ] = 2*x[2*i-1]for (i=0; i<n; i++) { x[2*i+1] = 2*x[2*i]
Pingali: Constraints as closure operators
x
Store of logic variables: lattice, ordered by information order. Top element = false …
Programs = extensive, idempotent operators on store
Composition = least upper bound of closure operators [f || g] (x) = LUB { x , f(x), g(f(x)), f(g(f(x)))…..
x = array(2*n), x[0] = 1for (i=1; i<n; i++) { x[2*i ] = 2*x[2*i-1]for (i=0; i<n; i++) { x[2*i+1] = 2*x[2*i]
Closure operators via fixed points
xClosure operator f determined by the set of fixed points FIX(f)
FIX(f||g) : set intersection of FIX(f), FIX(g)
x = array(2*n), x[0] = 1for (i=1; i<n; i++) { x[2*i ] = 2*x[2*i-1]for (i=0; i<n; i++) { x[2*i+1] = 2*x[2*i]
Aside: Expressions. Input/Output Symmetry
Interpret a function Array() Array() as a closure operator on [ Store x Array1 x Array2]
Array1, Array2: Copies of Domain of arrays Store: Binding of variables to values (perhaps arrays) All ordered by information ordering
array
array
array array
Research into (concurrent) constraint programming Generalizing shared store.
Weakening monotonicity
Adding time
Shared Store == Constraint system
[Lassez, Maher][Panangaden, Saraswat, Scott, Seely]
Conjunction
Existentials
A database of logical facts.
Eg. HERBRANDT, RATIONAL TREES, SET CONSTRAINTS
Concurrent constraint programming
[Saraswat][Panangaden, Rinard, Saraswat][Palamidessi, de Boer, …]
[TELL] a: add c to store
[ASK] if a then A: [blocking] query for a
[PARALLEL]: A || B
Program execution as proof search
[Lincoln, Saraswat]
c A: implication
A || B: conjunction
Aside: Uniform proofs [Miller, Nadathur,Loveland…]
An INTUITIONIST proof in which any sequent whose succeedent contains a non-atomic formula occurs only as the result of an inference rule that introduces the top level logical symbol of that formula, eg.
Horn Clauses
Lambda Prolog
18
BaseD ::= true | D and D G ::= true | G and G | G or G | exists X G
Recursive QueryD::= G-> A G::= AD::= forall X D
Constraint Query G::= c
eXtensible Query G::= D->G
Generic Query G::= forall X G
Recursive AgentD::= E | E -> D | t=tD::= forall X D
Tell AgentD::= c
Ask AgentD::= G-> D
LPConc LP
Conc LP w/ Tell
CCP
CLP
HH
HH CLP
Deep CCP
HH CCP
Deep CCP = CLP + CCPHH CLP = HH + CLPHH CCP = HH + CLP + CCP
1983 1977
1987 1987
19911991
2005 FSTTCS
2003
Kowalski, Colmerauer,…
Jaffar, Lassez, Maher
Miller, Nadathur
Clark,
Shapiro, Ueda
Maher, Saraswat
Saraswat, Lincoln
Leach, Nieva, Rodriguez-Artalejo
V. Saraswat
(Some) Logic Programming Languages 1977-2005 Saraswat, Nadathur, Jagadeesan
Default Logic
The “Histogram” problem [PINGALI]
Given: A[1..n] taking values in 1..mCompute IN PARALLEL : B[1..m] such that B[j] = {i | A[i] = j}
Default CC [TELL] a:
[ASK] if a then A
[PARALLEL]: A || B
[DEFAULT] if a else A
Default CC: flavors of indeterminacy
if a ELSE a NO SOLUTIONS
if a ELSE b, if b ELSE a TWO SOLUTION
Default CC [TELL] a:
[ASK] if a then A
[PARALLEL]: A || B
[DEFAULT] if a else A
Logic: Reiter’s default logicProof search interpretation of default cc not explored.
Ma: if a else a
Time!
Model
P0
P1
P2
P3
Store is reborn at each instant
At each instant: synchrony
Run program to quiescence to get current store and a continutation for the future
HENCE A = NEXT ( ALWAYS ( A))
Payoff: an analysis of synchronous programming [Berry, Benveniste]
The multiform nature of time . ``Any signal can serve as a notion of time’’
TIME A ON a: A runs only at those instants when store entails “a”
Payoff: an analysis of synchronous programming [Berry, Benveniste]
The multiform nature of time . ``Any signal can serve as a notion of time’’
do A watching a: A runs only at those instants when store entails “a”
Payoff: an analysis of synchronous programming [Berry, Benveniste]
The multiform nature of time . ``Any signal can serve as a notion of time’’
suspend A on a activate b: A runs only at those instants when store entails “a”
Payoff: an analysis of synchronous programming
Causality issues in synchronous programming ==== Determinacy issues of default logic
TCC for complex event processingPAPER IN PROCEEDING
Examples Declare the sensor as faulty if no reading has been received for 500ms
Every tenth time the price drops within an hour emit volatility warning.
Sea of asynchronous events, correlate different event streams, detect absence of events
permit aggregations over sliding windows, specify dependent sliding windows
Liberating programmer from forward-looking and event-driven rules
Maintaining the past information. [Nielsen, Palamidessi, Valencia]
Moving “back-and-forth” in the past
``Order a review if the last time that IBM stock price dropped by $10 in a day, there was more than $20 increase in trading volume for Oracle the following day."
“If the merchant has been tenured less than 90 days, and the sum of the transactions in the last 7 days is much higher than the 7 day average for the last 90 days, then investigate a 7 day hit and run possibility.”
THE PAPER
An operational semantics
Conservativity over Timed CC
QUESTIONS?
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