Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. UPPAAL’s Modeling and Specification Language & Philips Bounded Retransmission Protocol Paul Pettersson

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Timed Automata n m a (Alur & Dill, 1990) Clocks: x, y x 3 x := 0 Guard Boolean combination of comp with integer bounds Reset Action perfumed on clocks Transitions ( n, x=2.4, y= ) ( n, x=3.5, y= ) e(1.1) ( n, x=2.4, y= ) ( m, x=0, y= ) a State ( location, x=v, y=u ) where v,u are in R Action used for synchronization

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. n m a Clocks: x, y x 3 x := 0 Transitions ( n, x=2.4, y= ) ( n, x=3.5, y= ) e(1.1) ( n, x=2.4, y= ) e(3.2) x<=5 y<=10 Location Invariants g1 g2 g3 g4 Timed Safety Automata = Timed Automata + Invariants (Henzinger et al, 1992)

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Networks of Timed Automata + Integer Variables + arrays …. l1 l2 a! x>=2 i==3 x := 0 i:=i+4 m1 m2 a? y<=4 …………. Two-way synchronization on complementary actions. Closed Systems!

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Timed Automata in U PPAAL Timed (Safety) Automata + urgent actions + urgent locations + committed locations + data-variables (with bounded domains) + arrays of data-variables + constants + guards and assignments over data-variables and arrays… + templates with local clocks, data-variables, and constants.

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Declarations in U PPAAL clock x 1, …, x n ; int i 1, …, i m ; chan a 1, …, a o ; const c 1 n 1, …, c p n p ; Examples: clock x, y; int i, J0; int[0,1] k[5]; const delay 5, true 1, false 0; Array k of five booleans.

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Timed Automata in U PPAAL n m a x 3 x := 0 x<=5 y<=10 g1 g2 g3 g4 clock natural number and clock guards data guards clock assignments location invariants

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Urgent Channels urgent chan hurry; Informal Semantics: There will be no delay if transition with urgent action can be taken. Restrictions: No clock guard allowed on transitions with urgent actions. Invariants and data-variable guards are allowed.

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Urgent Locations Click “Urgent” in State Editor. Informal Semantics: No delay in urgent location. Note: the use of urgent locations reduces the number of clocks in a model, and thus the complexity of the analysis.

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Committed Locations Click “Committed” in State Editor. Informal Semantics: No delay in committed location. Next transition must involve automata in committed location. Note: the use of committed locations reduces the number of clocks in a model, and allows for more space and time efficient analysis.

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. UPPAAL Specification Language A[] p (AG p) E<> p (EF p) p::= a.l | g d | g c | p and p | p or p | not p | p imply p | ( p ) clock guardsdata guardsprocess location

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Philips Bounded Retransmission Protocol [D’Argenio et.al. 97]

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Protocol Overview Protocol developed by Philips. Transfer data between Audio/Video components via infra-red communication. Data files sent in smaller chunks. Problem: Unreliable communication medium. Sender retransmit if receiver respond too late. Receiver abort if sender sends too late.

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Overview of BRP SenderReceiver SR K L Input: file = p 1, …, p n lossy Output: p 1, …, p n BRP pipi ack

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. How It Works Sender input: file = p 1, …, p n. S sends (p 1, FST, 0 ), (p 2, INC, 1 ), …, (p n-1, INC, 1 ), (p n, OK, 0 ). R sends: ack, …, ack. S retransmits p i if timeout. Receiver recives: p 1, …, p n. Sender and Receiver receives NOK or OK. whole file OK more parts will follow first part of file

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. BRP Model Overview SenderReceiver SR K L Input: file = p 1, …, p n ack (p i,INDication,abit ) lossy ok, nok, dk IND, ok, nok Output: p 1, …, p n BRP

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. The Lossy Media value-passing lossy = may drop messages one-place capacity delay

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Bounded Retransmission S sends a chunk pi and waits for ack from R. If timeout the chunk is retransmitted. If too many timeout the transmission fails ( NOK is sent to Sender ). If whole file successfully sent OK is sent to Sender. Receiver is similar.

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Process S

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. Process R

Real-Time Systems, DTU, Feb 29, 2000 Paul Pettersson, BRICS, Aalborg, Denmark. The Sender and Receiver