TU / e /AIS Group Technische Universiteit Eindhoven University of Technology Modeling Grid Workflows with Colored Petri Nets Carmen Bratosin, Wil van der Aalst, and Natalia Sidorova

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'072 What is a Grid? A world wide distributed infrastructure composed by heterogeneous resources linked by common standards. Status 1. Grid technologies available: Globus, Condor, OGSA-DAI, Taverna etc. 2. Workflows for organizing the job flow

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'073 Grid architecture User processes Middleware Resources layer User requests Resource information Resource ids Job descriptions

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'074 Resources colset Props = list Prop; colset ResID = string; colset Res = product ResID * Props * Props; - Computing or Storage Elements - Characterized by a set of properties: e.g. CPU etc.

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'075 Grid Workflow Two different types of elements: Jobs running Control elements

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'076 Grid jobs Requirements: minimal set of properties that a resource should fulfill Running job: characterized by process instance id and the allocated resource id

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'077 Middleware fun en((rid,free,busy),req) = m_leq(req,free); fun take((rid,free,busy),req) = (rid,m_min(free,req),m_add(busy,req)); fun return((rid,free,busy),req) = (rid,m_add(free,req),m_min(busy,req));

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'078 Patterns: multiple allocation

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'079 Patterns: multiple allocation

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'0710 Process mining example

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'0711

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'0712

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'0713 Verification of grid workflows Two steps process: 1. Structural verification without resource constraints 2. Structural verification with resource constraints

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'0714 Verification of grid workflows: Step 1 (“infinite” resources) Wanted property: soundness Two additional conditions:  the marking of the requirements places remains the same for all the reachable markings and  the resource pool place marking in the final state has the same value as in the initial state. Home Properties Home Markings [28] Liveness Properties Dead Markings [28] Dead Transition Instances None Live Transition Instances None

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'0715 Verification of grid workflows: Step 1 Wanted property: soundness Two additional conditions:  the marking of the requirements places remains the same for all the reachable markings and  the resource pool place marking in the final state has the same value as in the initial state. Home Properties Home Markings [28] Liveness Properties Dead Markings [28] Dead Transition Instances None Live Transition Instances None

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'0716 Verification of grid workflows: Step 2 limited amount of resources Wanted property: no deadlocks Analysis of a grid model with multiple instances and a limited set of resources Home Properties Home Markings None Liveness Properties Dead Markings [420,456,952]

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'0717 Correcting process mining workflow Identified problem: multiple resources are claimed without being released Solution: Claiming/releasing more resources

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'0718

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'0719

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology October 22-24, 2007 Aarhus, Denmark CPN'0720 Conclusions A structural method to design grid workflows CPN Tools helped in finding model problems Future work Extend the model with time Extend model such that resources can become unreliable Analysis of different allocation policies base d on resource history