CS476 Program Verification

Spring 2020

Time: Tuesday and Thursday, 9:30-10:45

Place: Siebel Center 1131

Professor: Jose Meseguer

Office Hours: Immediately following class in Dr. Meseguer's office.


Reading Materials


Comprehensive Final (due: May 11)


Grading

The course will consist of weekly homework assignments and one long homework assignment towards the end covering a wide range of the course material. Each problem on each homework will be worth 10 points, and the homeworks all together will be worth 70% of the grade. The final comprehensive homework assignment will be worth 30% of the grade.

If you are taking the class for 4 credits, then there will also be a final project for the course. The final project must be turned in by the assigned final date before a grade for the class will be issued.

Homework

Homework 1 (due: Jan 30)

PDF

Homework 2 (due: Feb 6)

PDF

Homework 3 (due: Feb 13)

PDF

Maude module

Homework 4 (due: Feb 25)

PDF

Maude module

Homework 5 (due: Mar 3)

PDF

Maude module

Homework 6 (due: Mar 10)

PDF

Homework 7 (due: Mar 24)

PDF

Homework 8 (due: Mar 31)

PDF

NAT module

NAT+DIST module

Homework 9 (due: Apr 7)

PDF

Homework 10 (due: Apr 14)

PDF

SORTING module

DIN-PHIL module

Homework 11 (due: Apr 21)

PDF

PERMUTATIONS

Homework 12 (due: Apr 28)

PDF

COMMUNICATION

Homework 13 (due: May 5)

PDF

SIMPLE-SYS


Lectures

Lecture 01 - Jan 21, 2020

Lecture Slides

Lecture 02 - Jan 23, 2020

Lecture Slides

Lecture 03 - Jan 28, 2020

Lecture Slides

Lecture 04 - Jan 30, 2020

Lecture Slides

Lecture 05 - Feb 6, 2020

Lecture Slides

Lecture 06 - Feb 11, 2020

Lecture Slides

Lecture 07 - Feb 13, 2020

Lecture Slides

Lecture 08 - Feb 18, 2020

Lecture Slides

Lecture 09 - Feb 20, 2020

Lecture Slides

Lecture 10 - Feb 25, 2020

Lecture Slides

Lecture 11 - Feb 27, 2020

Lecture Slides

Lecture 12 - Mar 05, 2020

Lecture Slides

Appendix

Lecture 13 - Mar 10, 2020

Lecture Slides

Lecture 14 - Mar 12, 2020

Lecture Slides

Lecture 15 - Mar 24, 2020

Lecture Slides

Recording

Lecture 16 - Mar 26, 2020

Lecture Slides

Recording

Lecture 17 - Mar 31, 2020

Lecture Slides

Recording 1

Recording 2

Lecture 18 - Apr 02, 2020

Lecture Slides

Recording

Lecture 19 - Apr 07, 2020

Lecture Slides

Recording

Lecture 19.5 - Apr 09, 2020

Lecture Slides

Recording

Lecture 20 - Apr 14, 2020

Lecture Slides

Appendix

Recording

Lecture 20.5 - Apr 16, 2020

Lecture Slides

Recording

Lecture 21 - Apr 21, 2020

Lecture Slides

Recording

Lecture 22 - Apr 23, 2020

Lecture Slides

Recording

Lecture 23 - Apr 28, 2020

Lecture Slides

Recording

Lecture 24 - Apr 30, 2020

Lecture Slides

Recording

Lecture 25 - May 5, 2020

Lecture Slides - 1

Lecture Slides - 2


Maude

Maude will be the primary tool used in this course, but several tools/libraries written in Maude will also be used. Some of these libraries require extra functionality to be added directly to Maude (at the C++ level). You can choose to build from the Maude sources or directly from binary releases of Maude 2.7.1.

# Download and unzip Maude 2.7.1 binary release for Linux
$ wget 'https://github.com/maude-team/maude/releases/download/v2.7.1-ext-hooks/maude-2.7.1-linux.tar.gz'
$ tar -xvf maude-2.7.1-linux.tar.gz
# Download Maude 2.7.1 binary release for MacOS
$ wget 'http://maude.cs.illinois.edu/w/images/2/25/Maude-2.7.1-osx.zip'
$ unzip Maude-2.7.1-osx.zip
# Run Maude
$ ./maude
\||||||||||||||||||/
--- Welcome to Maude ---
/||||||||||||||||||\
Maude 2.7.1 built: Aug 31 2016 18:22:38
Copyright 1997-2016 SRI International
Sun Oct 1 11:59:31 2017
Maude>

Maude Formal Environment (MFE)

The MFE packages together several tools which will be used in the course. It's recommended that you use the binary releases for anything needing the MFE. To get setup using MFE, you might do:

# Clone MFE
$ git clone 'https://github.com/maude-team/mfe'
# Launch Maude with MFE
$ ./maude mfe/src/mfe.maude
\||||||||||||||||||/
--- Welcome to Maude ---
/||||||||||||||||||\
Maude 2.7.1 built: Aug 31 2016 18:22:38
Copyright 1997-2016 SRI International
Sun Oct 1 11:51:55 2017
Full Maude 2.7e September 22th 2016
The Maude Formal Environment 1.0b
Inductive Theorem Prover - July 20th 2010
Sufficient Completeness Checker 2a - August 2010
Church-Rosser Checker 3p - August 30th 2016
Coherence Checker 3p - August 30th 2016
Maude Termination Tool 1.5j - August 11th 2014
Maude>

Note that many of the tools in the MFE cannot reason with built-in modules (many of the modules which come in prelude.maude). By default though, Maude includes the built-in module BOOL with any user-defined module. If you get the following error:

Error The use of built-ins is not supported by the checker.

be sure to disable including BOOL into your module by default:

set include BOOL off .

fmod MYMODULE is
    ...
endfm

If you are in loop mode (eg. if you have already loaded the MFE), then you must do this in parentheses:

(set include BOOL off .)

(fmod MYMODULE is
    ...
 endfm)

Sufficient Completeness Checker

The SCC tool works on an older version of Maude, and I only know of Linux binaries for it. Login to EWS or use a virtual machine if you are not on a Linux machine.

$ wget 'http://maude.cs.uiuc.edu/tools/scc/releases/Maude-ceta-2.3-linux.tgz'
$ tar -xvf Maude-ceta-2.3-linux.tgz
$ cd Maude-ceta-2.3-linux
$ ./maude-ceta
\||||||||||||||||||/
--- Welcome to Maude ---
/||||||||||||||||||\
Maude-ceta 2.3 built: Feb 18 2007 09:49:47
Copyright 1997-2007 SRI International
With CETA extensions Copyright 2006-2007
University of Illinois at Urbana-Champaign
Mon Oct 2 19:17:22 2017
# Load SCC
Maude> load scc.maude
# Start the SCC
Maude> loop init-cc .
Starting the Maude Sufficient and Canonical Completeness Checker.
# Load the file with module of interest (note that it should NOT be in parens)
Maude> load ../../../PATH/TO/FILE/WITH/MODULE/NOT/IN/PARENTHESES
# Select the CC-LOOP module.
Maude> select CC-LOOP .
# Check Sufficient Completeness (modulo other proof goals)
Maude> (scc MODULE-OF-INTEREST .)
Warning: no loop state.
Advisory: attempting to reinitialize loop.
Starting the Maude Sufficient and Canonical Completeness Checker.
Checking sufficient completeness of MODULE-OF-INTEREST ...
Success: MODULE-OF-INTEREST is sufficiently complete under the assumption that it is ground weakly-normalizing, confluent, and ground sort-decreasing.

Maude Inductive Theorem Prover

Go to the Maude ITP Webpage to download the sources for the Maude ITP. The Maude ITP runs on Maude 2.7.

Commands that you may find useful (see the tutorial on the Maude ITP website):

Using the example module from lecture 13 (say file nat-ord.maude):

fmod NATURAL-ORD is
  sort Natural .
  op 0 : -> Natural [ctor] .
  op s : Natural -> Natural [ctor] .
  op _<_ : Natural Natural -> Bool .
  op _=<_ : Natural Natural -> Bool .
  vars N M : Natural .
  eq N < 0 = false .
  eq 0 < s(N) = true .
  eq s(N) < s(M) = N < M .
  ceq N =< M = true if N < M .
  ceq N =< M = true if not(M < N) .
  ceq N =< M = false if M < N .
endfm

And an example interaction:

# Download and unpack the Maude itp
$ wget 'http://maude.cs.uiuc.edu/tools/itp/maude_itp.tar.gz'
$ tar -xvf maude_itp.tar.gz
\||||||||||||||||||/
--- Welcome to Maude ---
/||||||||||||||||||\
Maude 2.7 built: Oct 17 2017 22:51:54
Copyright 1997-2014 SRI International
Tue Oct 17 23:40:31 2017
Maude> load maude_itp/itp-tool.maude
Maude> load nat-ord.maude
Maude> select ITP-TOOL .
Maude> loop init-itp .
ITP tool (May 25th, 2006)
--- Introduce linearity goal
--- ------------------------
Maude> (goal linear : NATURAL-ORD |- A{N:Natural ; M:Natural} (((N =< M) or (M =< N)) = (true)) .)
rewrites: 1200 in 18ms cpu (18ms real) (66666 rewrites/second)
=================================
label-sel: linear@0
=================================
A{M:Natural ; N:Natural}
N:Natural =< M:Natural or M:Natural =< N:Natural = true
+++++++++++++++++++++++++++++++++
--- Use lemma of constants
--- ----------------------
Maude> (cns .)
rewrites: 223 in 3ms cpu (2ms real) (74333 rewrites/second)
New goals:
=================================
label-sel: linear@0
=================================
N*Natural =< M*Natural or M*Natural =< N*Natural = true
+++++++++++++++++++++++++++++++++
--- Split on N < M
--- --------------
Maude> (split on (N*Natural < M*Natural) .)
rewrites: 222 in 5ms cpu (5ms real) (44400 rewrites/second)
New goals:
=================================
label-sel: linear@1.0
=================================
N*Natural =< M*Natural or M*Natural =< N*Natural = true
=================================
label: linear@2.0
=================================
N*Natural =< M*Natural or M*Natural =< N*Natural = true
+++++++++++++++++++++++++++++++++
--- Discharge goal 1 with assumptions
--- ---------------------------------
Maude> (auto .)
rewrites: 112 in 0ms cpu (0ms real) (~ rewrites/second)
Eliminated current goal.
New current goal:
=================================
label-sel: linear@2.0
=================================
N*Natural =< M*Natural or M*Natural =< N*Natural = true
+++++++++++++++++++++++++++++++++
--- Discharge goal 2 with assumptions
--- ---------------------------------
Maude> (auto .)
rewrites: 54 in 0ms cpu (0ms real) (~ rewrites/second)
Eliminated current goal.
q.e.d
+++++++++++++++++++++++++++++++++

RLTool Command Overivew

Here is the command listing from rltool-lib.maude in the tool archive.

RLTool

sort @QFForm@ @QFCTerm@ @NeQFCTermSet@ @Term@ @TermSet@ @ReachFormEx@ @LabelReachFormEx@ .
subsort @QFCTerm@ < @NeQFCTermSet@ .
subsort @Term@ < @TermSet@ .
op ((_))     : @Bubble@                      -> @Term@ [ctor] .
op _U_       : @TermSet@ @TermSet@           -> @TermSet@ [assoc comm ctor] .
op true      :                               -> @QFForm@ [ctor] .
op (_)=(_)   : @Bubble@ @Bubble@             -> @QFForm@ [ctor] .
op (_)=/=(_) : @Bubble@ @Bubble@             -> @QFForm@ [ctor] .
op _/\_      : @QFForm@ @QFForm@             -> @QFForm@ [prec 58 assoc comm ctor] .
op _\/_      : @QFForm@ @QFForm@             -> @QFForm@ [prec 59 assoc comm ctor] .
op (_)|_     : @Bubble@ @QFForm@             -> @QFCTerm@ [prec 60 ctor] .
op _\/_      : @NeQFCTermSet@ @NeQFCTermSet@ -> @NeQFCTermSet@ [prec 61 assoc comm ctor] .
op _=>_      : @NeQFCTermSet@ @NeQFCTermSet@ -> @ReachFormEx@ [prec 62 ctor] .
op _:_       : @Token@ @ReachFormEx@         -> @LabelReachFormEx@ [prec 63 ctor] .

sort MetaRLTLCommand .
--- module/var/backend setup
op select_.               : @Token@ -> MetaRLTLCommand [ctor] .
op select-rls_.           : @NeTokenList@ -> MetaRLTLCommand [ctor] .
op declare-vars_.         : @TermSet@ -> MetaRLTLCommand [ctor] .
op use`tool_for_on_.      : @Token@ @Token@ @Token@ -> MetaRLTLCommand [ctor] .
op use`tool_for_on_with_. : @Token@ @Token@ @Token@ @NeTokenList@ -> MetaRLTLCommand [ctor] .

--- goal/term state setup
op def-term-set_.         : @NeQFCTermSet@ -> MetaRLTLCommand [ctor] .
op add-goal_.             : @LabelReachFormEx@ -> MetaRLTLCommand [ctor] . --- add as goal and axiom
op add-goal!_.            : @LabelReachFormEx@ -> MetaRLTLCommand [ctor] . --- add as goal
op add-axiom_.            : @LabelReachFormEx@ -> MetaRLTLCommand [ctor] . --- add as axiom TODO: revisit this command
op inv_to_with_on_.       : @Token@ Qid @TermSet@ @NeQFCTermSet@ -> MetaRLTLCommand [ctor] .
op inv_to_on_.            : @Token@ Qid @NeQFCTermSet@ -> MetaRLTLCommand [ctor] .

--- finish setup
op start-proof`.          : -> MetaRLTLCommand [ctor] .

--- proof manipulation
--- apply basic proof strategy
op auto_.                 : Nat -> MetaRLTLCommand [ctor] .
op auto*`.                : -> MetaRLTLCommand [ctor] .
op auto`.                 : -> MetaRLTLCommand [ctor] .
--- delete unwanted goals
op focus_.                : NeSet{Nat} -> MetaRLTLCommand [ctor] .
op focus_.                : @Term@ -> MetaRLTLCommand [ctor] .
op focus_.                : @QFCTerm@ -> MetaRLTLCommand [ctor] .
op focus_/_.              : @QFCTerm@ @QFCTerm@ -> MetaRLTLCommand [ctor] .
--- change axioms used
op use-axioms_on_.        : @NeTokenList@ Nat -> MetaRLTLCommand  [ctor] .               --- modify goal to use circularities
op use-axioms_._on_.      : @NeTokenList@ @NeTokenList@ Nat -> MetaRLTLCommand  [ctor] . --- modify goal to use axioms/circularities
--- do case analysis a variable
op case_on_by_.           : Nat @Token@ @TermSet@ -> MetaRLTLCommand [ctor] .
op case_on_by_.           : @Term@ @Token@ @TermSet@ -> MetaRLTLCommand [ctor] .
op case_on_by_.           : @QFCTerm@ @Token@ @TermSet@ -> MetaRLTLCommand [ctor] .
--- split on a formula
op split_by_.             : Nat @QFForm@ -> MetaRLTLCommand [ctor] .
op split_by_.             : @Term@ @QFForm@ -> MetaRLTLCommand [ctor] .
op split_by_.             : @QFCTerm@ @QFForm@ -> MetaRLTLCommand [ctor] .
op replace_by_.           : Nat @QFForm@ -> MetaRLTLCommand [ctor] .
op replace_by_.           : @Term@ @QFForm@ -> MetaRLTLCommand [ctor] .
op replace_by_.           : @QFCTerm@ @QFForm@ -> MetaRLTLCommand [ctor] .
op split_by_and_.         : Nat @QFForm@ @QFForm@ -> MetaRLTLCommand [ctor] .
op split_by_and_.         : @Term@ @QFForm@ @QFForm@ -> MetaRLTLCommand [ctor] .
op split_by_and_.         : @QFCTerm@ @QFForm@ @QFForm@ -> MetaRLTLCommand [ctor] .
--- try to close a set of goals with default strategy---but do nothing if this process fails
op try-finish_.           : NeSet{Nat} -> MetaRLTLCommand [ctor] .
op try-finish_.           : @QFCTerm@ -> MetaRLTLCommand [ctor] .
op try-finish_/_.         : @QFCTerm@ @QFCTerm@ -> MetaRLTLCommand [ctor] .
--- try to subsume a goal by another
op subsume_by_.           : Nat Nat -> MetaRLTLCommand [ctor] .
--- resume from a debugging output pause
op continue`.             : -> MetaRLTLCommand [ctor] .
--- delete inactive goals
op delete-inactive`.      : -> MetaRLTLCommand [ctor] .

--- output commands
op show-goal-table`.           : -> MetaRLTLCommand [ctor] .
op show-goal-ids`.             : -> MetaRLTLCommand [ctor] .
op show-all-goal-ids`.         : -> MetaRLTLCommand [ctor] .
op show-goals_.                : NeSet{Nat} -> MetaRLTLCommand [ctor] .
op show-goals`.                : -> MetaRLTLCommand [ctor] .
op show-level_.                : Nat -> MetaRLTLCommand [ctor] .
op show-levels`.               : -> MetaRLTLCommand [ctor] .
op show-ancestors_generation_. : NeSet{Nat} Bound -> MetaRLTLCommand [ctor] .
op show-narrowings_.           : Nat -> MetaRLTLCommand [ctor] .
op show-maude-cmd_on_.         : @Token@ Nat -> MetaRLTLCommand [ctor] .