[isabelle] new AFP entries

We are pleased to announce two new entires in the Archive of Formal Proofs 

Benjamin Porter:
Cauchy's Mean Theorem and the Cauchy-Schwarz Inequality 

 This document presents the mechanised proofs of two popular theorems
 attributed to Augustin Louis Cauchy - Cauchy's Mean Theorem and the
 Cauchy-Schwarz Inequality. 


Damián Barsotti: 
Instances of Schneider's generalized protocol of clock synchronization.

 F. B. Schneider ("Understanding protocols for Byzantine clock
 synchronization'') generalizes a number of protocols for Byzantine
 fault-tolerant clock synchronization and presents a uniform proof
 for their correctness. In Schneider's schema, each processor
 maintains a local clock by periodically adjusting each value to one
 computed by a convergence function applied to the readings of all
 the clocks. Then, correctness of an algorithm, i.e. that the
 readings of two clocks at any time are within a fixed bound of each
 other, is based upon some conditions on the convergence function. To
 prove that a particular clock synchronization algorithm is correct
 it suffices to show that the convergence function used by the
 algorithm meets Schneider's conditions.
 Using the theorem prover Isabelle, we formalize the proofs that the
 convergence functions of two algorithms, namely, the Interactive
 Convergence Algorithm (ICA) of Lamport and Melliar-Smith and the
 Fault-tolerant Midpoint algorithm of Lundelius-Lynch , meet
 Schneider's conditions.  Furthermore, we experiment on handling some
 parts of the proofs with fully automatic tools like ICS and
 These theories are part of a joint work with Alwen Tiu and Leonor
 P. Nieto "Verification of Clock Synchronization Algorithms:
 Experiments on a combination of deductive tools'' in proceedings of
 AVOCS 2005 (http://users.rsise.anu.edu.au/~tiu/clocksync.pdf). In this
 work the  correctness of  Schneider schema was also verified using
 Isabelle (available at http://afp.sourceforge.net/entries/GenClock.shtml).


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