On secondment at

1
Six Months In Praxis
Bill J Ellis
Dependable Systems Group School of Mathematical
Computer Sciences Heriot-Watt University Edinburg
h

• (On secondment at)
• Praxis High Integrity Systems
• Bath

2
Overview

• Context
• NuSPADE
• Proposal
• Architecture
• Results
• SPADEase
• Proposal
• Conclusions

3
Context

• NuSPADE 2001 ? 2004
• EPSRC critical systems programme (GR/R24081)
• Collaboration with Praxis
• SPADEase Jan 2005 ? July 2005
• EPSRC research assistant industrial secondment
  scheme (GR/T11289/01)
• Direct follow-on to NuSPADE
• Secondment to Praxis
• PhD 2001 ? 2005?
• Research directly related to NuSPDE
• Now writing up
• Principle investigator (and PhD supervisor)
  Andrew Ireland

2001
2002
2003
2004
2005
2006
4
NuSPADE

• Investigate the role of proof planning within the
• SPARK approach to high integrity software
• Proof planning
• Strong paradigm for exploring proof techniques
• Previous results in proving loop verification
  conditions (VCs)
• SPARK approach to high integrity software
• Gain immediate access to VCs
• Potential for industrial analysis

5
Completing Proof in SPARK
Remaining VCs
SPADE Simplifier
SPADE User
Program properties
Proof Script
Code and specification
SPADE Proof Checker
6
Introducing NuSPADE
SPADE User
Remaining VCs
SPADE Simplifier
NuSPADE
Program properties
Proof Script
Program analyser
Proof planner
Code and specification
SPADE Proof Checker
7
NuSPADE Results

• NuSPADE
• Evaluation based on examples from literature and
  industrial data provided by Praxis (SHOLIS)
• Focus on
• Exception freedom VCs
• Not automatically proved by the Simplifier
• Typically these arise from loop based code
• 80 of such problems were provable using our
  techniques
• However
• NuSPADE is a typical academic system

8
SPADEase

• Towards increased verification automation for
  high integrity software engineering
• Towards
• Six months is not long enough for a complete
  system
• Increased verification automation
• Exploit the results of the NuSPADE project
• With an emphasis the practical task of automation
• High integrity software engineering
• Secondment at Praxis (High Integrity Systems)

9
Introducing SPADEase
VCG

• SPADEase
• Automatically prove additional VCs
• Same external behaviour as the Simplifier
• Focus on proof planning (over program analysis)
• Implementation
• Tweaks to Simplifier (completed)
• Tweaks to Proof Checker (first draft completed)
• Overhaul of NuSPADE (just starting)
• Problem loading mechanism
• Data management system
• Evaluation
• Compare with NuSPADE
• Explore new examples

SPADEase
SPADE Simplifier
SIV
Refined NuSPADE
SIV
10
Conclusions

• Building upon NuSPADE
• To develop a new SPADE proof tool (SPADEase)
• Feedback welcome
• Training opportunities?
• Interesting proof examples?
• http//www.macs.hw.ac.uk/spadease/