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Formal Modelling in VDM

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Net Meeting 72

Date 30th June 2013
Participants Augusto Ribeiro, Hiroshi Sako, John Fitzgerald, Marcel Verhoef, Nick Battle, Peter Gorm Larsen, Peter Jorgensen, Shin Sahara, Luis Couto (minutes)

Review Status of the Action List

The action item list is maintained as a tracker on SourceForge.

Overture Language Board Status

No LB meeting since the last time, though a paper is being worked on.

Status of VDMTools Development

Newest Version

The VDM Toolbox 9.0.3- Fri 14-June-2013

Measure functions became executable. And, we can check return values decrease.

Following is a sample: Based on LRM sample. Current checking checks return value is smaller than old one. For example, if n.#1 of id2 changed to n.#2 then runtime error occurs. — class A

operations public Test: () ==> seq of nat Test() ==

return [

functions public fac: nat +> nat fac(n) ==

cases n:
  0      -> 1,
  others -> n * fac(n-1)

measure id;

public fac2: nat +> nat fac2(n) ==

cases n:
  0      -> 1,
  others -> n * fac3(n-1)

measure id;

public fac3: nat +> nat fac3(n) == fac2(n);

public fac4: (nat * nat) +> nat fac4(mk_(n, x)) ==

cases n:
  0      -> 1,
  others -> n * fac4(mk_(n-1, x))

measure id2;

public fac5: nat +> nat +> nat fac5(n)(x) ==

cases n:
  0      -> 1,
  others -> n * fac5(n-1)(x)

measure id3;

public fac6[@T]: @T +> @T fac6(n) ==

cases n:
  0      -> 1,
  others -> n * fac6[@T](n-1)

measure id4;

public fac7[@T]: @T +> @T +> @T fac7(n)(x) ==

cases n:
  0      -> 1,
  others -> n * fac7[@T](n-1)(x)

measure id5;

public id: nat +> nat id(n) == n;

public id2: (nat * nat) +> nat id2(n) == n.#1;

public id3: nat +> nat +> nat id3(n)(-) == n;

public id4[@T2]: @T2 +> nat id4(n) == n;

public id5[@T2]: @T2 +> @T2 +> nat id5(n)(-) == n;

end A

How to execute:

vpp> r test.vdm Parsing “test.vdm” (Plain Text) … done vpp> set measure              <— set measure execution measure check set vpp> init Initializing specification … Initializing A done vpp> d new A().Test() [ 3628800, 3628800, 3628800, 3628800, 3628800, 3628800 ] vpp> tcov write vdm.tc vpp> rtinfo vdm.tc

100%     22  A`id
100%     11  A`fac
100%     11  A`id2
100%     11  A`id3
100%     11  A`id4
100%     11  A`id5
100%      1  A`Test
100%     11  A`fac2
100%     10  A`fac3
100%     11  A`fac4
100%     11  A`fac5
100%     11  A`fac6
100%     11  A`fac7
100%  A

Total Coverage: 100% vpp> unset measure            <— stop measure execution measure check unset vpp> tcov reset vpp> d new A().Test() [ 3628800, 3628800, 3628800, 3628800, 3628800, 3628800 ] vpp> tcov write vdm.tc vpp> rtinfo vdm.tc

  0%      0  A`id
100%     11  A`fac
  0%      0  A`id2
  0%      0  A`id3
  0%      0  A`id4
  0%      0  A`id5
100%      1  A`Test
100%     11  A`fac2
100%     10  A`fac3
100%     11  A`fac4
100%     11  A`fac5
100%     11  A`fac6
100%     11  A`fac7
 94%  A

Total Coverage: 94% vpp>

These new tests have not yet been tried on VDMJ/Overture. Nick will be handling this. Also, Shin will try the additional tests for this in Overture.

The goal is for closer synchronization between both tools.

Status of the Overture Components


A few more small bugs fixed this period. A fix to type accessibility checks, a fix to restore coverage tracking for atomic statements, an improvement to class invariant handling, and a type-check correction for access to fields of object references passed as parameters. I think these have been copied into the ASTv2 branches now. There were also a couple of late fixes to the PO generator, following from work I’m doing with Luis, but those probably won’t have made it into ASTv2 yet.

Misc Fixes

Kenneth and Peter have fixed various small issues with the tool. Also, all the changes made to VDMJ have been ported to ASTv2. Except for the ongoing work on POG, which must be ported when it has reached a steady state in VDMJ. In addition, Overture has some issues with respect to coverage coloring that needs to be checked into. For some language constructs the coverage coloring is not handed correctly.


Work on the new POG by Luis and Nick is ongoing. Only a few obligations are left to be converted. The next stage will be testing.

Development Board Status

Module Reps

The Dev board continues to discuss the assignment of modules to the various rep. Progress is ongoing.

Overture Dev Night

Members of the Dev Board are planning an informal coding social event called Overture Dev night for September in Aarhus. More information will be available soon.

Release Planning

Overture 2.0.0

Status for the full release is essentially the same; JWC hasn’t had the opportunity to fully focus on this during the past month. Factoring out the bits that require Java7 has only had slow progress.

Remaining work includes:

We still plan to release during the summer, but it won’t be until August.

Overture 1.2.x

As before; expect a version 1.2.5 concurrent with the final 2.0.0

AstCreator split out

It is still planned to split AstCreator into a separate repository, but no progress has been made.

Community Maintenance Reporting


Still no new members. Tasks and responsibilities must be rethought.


We must discuss which tasks to prioritize and which responsibilities to keep/drop.

I propose wiki maintenance as the most important responsibility and as such the one that must kept. The blog/etc. will have to be dropped for now.

In terms of tasks, there are 3:

  1. wiki clean up
  2. website redesign
  3. web presence overhaul.

The first one is again the most important but it would be very nice if we could complete 2 and 3 in time for the release of Overture 2.0 (the new website could be launched along with 2.0 to “celebrate”). Some help would be needed to complete all 3 in time.

No volunteers were available to help with these tasks. Luis will make a plan and proceed on his own.

Publications Status and Plans

Planned Publications has been cleaned up (titles, dates, etc.).

But further updating is necessary on the status of some papers. Their authors (namely Sune) will be contacted to do so.

Also, some papers will be moved from In Press to Recently Appeared and their links updated (Shin and PGL).

Any Other Business

It has been proposed that the next NetMeeting (August 25) be held at the Overture workshop instead (1 week later). The idea was approved but we must coordinate with the organizers of the Overture workshop.

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