Systems Modeling and Analysis Using Colored Petri Nets Vijay Gehlot Center of Excellence in Enterprise Technology Department of Computing Sciences

Net-Centric Validation Conference CEET Conference Outline Introduction CPN Overview CPN Model of WMDNs SOA in Defense Presence/Discovery Model

Net-Centric Validation Conference CEET Conference Ariane 5 Failure Ariane 5, ESA Maiden Flight, 6/4/ sec later self-destructs Root cause: uncaught overflow exception

Net-Centric Validation Conference CEET Conference Mars Climate Orbiter Failure Mars Climate Orbiter, NASA Launched, 12/11/1998 Lost, 9/23/1999 Root cause: failed translation of English units into metric units in a segment of ground-based, navigation-related mission software

Net-Centric Validation Conference CEET Conference London Ambulance Service Failure Computer Aided Dispatch Introduced 10/26/1992 Within days major system failure  Vehicle positions incorrectly recorded  Multiple vehicles dispatched to same location  Severe delays  Lives lost

Net-Centric Validation Conference CEET Conference Airbus A320 Failure

Net-Centric Validation Conference CEET Conference Why Does This Matter? Computer systems perform many critical tasks Safety-critical systems will dominate Already complex nature of software SOAs and Net-centricity add dimensions of concurrent and distributed computations Systems for defense applications have very high dependability requirements Complex interactions that are hard to predict Consequences of failure  Injury, loss of life, environmental damage, financial loss, …  E.g, system downtime cost to brokerage operations: $7 Million/Hour  Cost of software defects: $200 Billion/Year

Net-Centric Validation Conference CEET Conference Current State From a recent report The Challenges of Complex IT Projects (Royal Academy of Engineering and British Computer Society): “The pace of technological change and the ferociously competitive nature of the industry lead to the triumph of speed over thoughtfulness, of the maverick shortcut over discipline, and the focus on the short term.”

Net-Centric Validation Conference CEET Conference Hope Robin Milner, a prominent computer scientist, in a lecture of January 2007: “The software industry [and the report] focuses on managing software production [process], not on understanding software itself [science of software]. … Grand Challenge: Establish modeling as the basis of informatics.”

Net-Centric Validation Conference CEET Conference Desire Keynote Address by Mark Schaeffer, Director, Systems & Software Engineering, Office of Under Secretary of Defense, Acquisition & Technology, IEEE Systems Conference, Honolulu, Hawaii, April 2007: “...System assurance is still a challenge … Use modeling and simulation to help refine warfighter concept of operations, system requirements, evaluate design alternative and identify constraints...”

Net-Centric Validation Conference CEET Conference An Example-Wireless Medical Device Networks Similar situations in defense and other settings too Modeled patient scenario with  Heart alarms  Pulse oxymeters alarms  Low battery alarms Used Colored Petri Nets

Net-Centric Validation Conference CEET Conference Colored Petri Nets Graphical modelling language Combination of Petri Nets and Programming Language Module support for hierarchical construction Support for both timed and untimed models Petri Nets: concurrency control structures synchronisation communication resource sharing CPN ML: data and manipulation compact modelling

Net-Centric Validation Conference CEET Conference Analysis CPN Tools software for model construction and analysis Interactive- and automatic simulation Application domain visualization Simulation-based performance analysis State space construction, analysis, and verification External process communication

Net-Centric Validation Conference CEET Conference CPN Model of WMDN

Net-Centric Validation Conference CEET Conference Results and Implications Need for QoS requirement for medical applications Similar situation in other application domains

Net-Centric Validation Conference CEET Conference Net-Centricity in DoD Context

Net-Centric Validation Conference CEET Conference SOA for DoD Applications Application characteristics include:  Presence/Availability awareness  Dynamic service discovery  Interoperable multiple connection types  Load balancing  … One implementation: SIP-based internal communications and information management Adds brokering, presence management and discovery capabilities to basic SOA

Net-Centric Validation Conference CEET Conference Example ESB Software Internals

Net-Centric Validation Conference CEET Conference CPN Model of a Key Presence/Discovery Component

Net-Centric Validation Conference CEET Conference Results Runtime Lab Output – Use case 1Model Output – Use case1

Net-Centric Validation Conference CEET Conference Related Modeling Efforts SOA Security SOA Compression SOA Governance SOA Granularity XMPP CPN as well as OPNET