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Mohamed G. Gouda                                        	CS 356
Spring 2008							Homework 2
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1. (Detecting Message Reorder: 5 points)

Consider a protocol where a process p continuously sends blocks of three 
messages each to process q. The three messages in a block are as follows:
first(integer), second(integer), and third(integer). Process p is specified
as follows:

process p
var data : array [integer] of integer,
    i    : integer
begin
     true -> send first(data[i]) to q; i := i+1;
             send second(data[i]) to q; i := i+1;
             send third(data[i]) to q; i := i+1;
end

Design process q such that q receives the sent messages and stores their 
integer fields in an infinite array rcvd in order. Process q should tolerate
message reorder, assuming that every sent message can take part in at most one
occurrence of reorder with an adjacent message in the channel from process p to
process q.		

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2. (5 points)

Consider a protocol that consists two process arrays p[i : 0..x-1] and 
q[j : 0..y-1]. Each p[i] can establish a connection to any q[j] using the
connection protocol in Section 6.1 such that each process can be involved in
at most one connection at a time. Processes p[i] and q[j] can be specified
partially as follows:

process p[i : 0..x-1]
const y
inp   m      : integer
var   conp   : boolean,           {init. false}
      cansnd : 0..m,		  
      peer   : 0..y-1

begin
    timeout ~conp ^ (for all j: 0<=j<n: #ch.p[i].q[j]+#ch.q[j].p[i]=0)
		  -> statement
[]  ...   
end

process q[j : 0..y-1]
const x
var   conq   : boolean,            {init. false}
      peer   : 0..x-1
par   i      : 0..x-1

begin
... 
end

Complete the specifications of processes p[i : 0..x-1] and q[j : 0..y-1].
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