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# Structured Occurrence Network for provenance: talk for ipaw12 paper

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IPAW'12 talk for this paper:
http://homepages.cs.ncl.ac.uk/paolo.missier/doc/IPAW12-SON.pdf

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### Structured Occurrence Network for provenance: talk for ipaw12 paper

1. 1. Modelling provenance using Structured Occurrence Networks Paolo Missier, Brian Randell, Maciej Koutny Newcastle University, UK IPAW’12 Santa Barbara, CA, June 2012Thursday, June 21, 2012
2. 2. Petri Nets and Occurrence Nets Historically, Occurrence Nets have been used to define process semantics of Petri Nets [2] IPAW 2012 - P.Missier [2] Best, Eike, and Raymond Devillers. “Sequential and concurrent behaviour in Petri net theory.” Theoretical Computer Science 55, no. 1 (1987): 87-136. http://www.sciencedirect.com/science/article/pii/0304397587900909. 2Thursday, June 21, 2012
3. 3. Occurrence Nets ON is about capturing causal relationships between events and conditions ON = (C, E, F ) with nodes C E and a ﬂow relation F ⊆ (C ×E)∪(E × C) satisfying the following: (i) for every condition c there is at most one event e such that (e,c) ∈ F, and at most one event f such that (c,f) ∈ F; (ii) for every event e there is at least one condition c such that (c, e) ∈ F , and at least one condition d such that (e, d) ∈ F ; (iii) ON forms an acyclic graph and F + is a partial order relation (the relation PrecON = (F ◦ F)|C×C is acyclic) IPAW 2012 - P.Missier 3Thursday, June 21, 2012
4. 4. Provenance and Occurrence Nets • "Provenance is defined as a record that • An Occurrence Net is an abstract record of describes the people, institutions, a single execution of some computing entities, and activities involved in system producing, influencing, or delivering a • Only information about causality and piece of data or a thing." [PROV] concurrency between events and visited local states is represented IPAW 2012 - P.Missier 4Thursday, June 21, 2012
5. 5. Provenance and Occurrence Nets • "Provenance is defined as a record that • An Occurrence Net is an abstract record of describes the people, institutions, a single execution of some computing entities, and activities involved in system producing, influencing, or delivering a • Only information about causality and piece of data or a thing." [PROV] concurrency between events and visited local states is represented Data: The evolution of variable A as a ON: IPAW 2012 - P.Missier 4Thursday, June 21, 2012
6. 6. Provenance and Occurrence Nets • "Provenance is defined as a record that • An Occurrence Net is an abstract record of describes the people, institutions, a single execution of some computing entities, and activities involved in system producing, influencing, or delivering a • Only information about causality and piece of data or a thing." [PROV] concurrency between events and visited local states is represented Data: The evolution of variable A as a ON: Agents: The evolution of Bob, the document editor: read drafted ready performed verified ptd paper internal to exp. results draft p1 memo IPAW 2012 - P.Missier read paper p2 4Thursday, June 21, 2012
7. 7. From ON to Structured ON ON is an adequate starting point, but extensions are needed to represent the activity of complex systems • Structured Occurrence Nets provide these extensions as new relationships amongst multiple ONs [2] IPAW 2012 - P.Missier [2] Koutny, M., and B Randell. “Structured Occurrence Nets: A Formalism for Aiding System Failure Prevention and Analysis Techniques.” Fundamenta Informaticae 97 (2009). 5Thursday, June 21, 2012
8. 8. From ON to Structured ON ON is an adequate starting point, but extensions are needed to represent the activity of complex systems • Structured Occurrence Nets provide these extensions as new relationships amongst multiple ONs [2] IPAW 2012 - P.Missier [2] Koutny, M., and B Randell. “Structured Occurrence Nets: A Formalism for Aiding System Failure Prevention and Analysis Techniques.” Fundamenta Informaticae 97 (2009). 5Thursday, June 21, 2012
9. 9. Provenance modelling patterns using SON Main goal of this work: to explore the use of Structured Occurrence Nets as a formal model of provenance • Data is viewed as an evolving system • Agents are also evolving systems, thus their evolution is also captured • Uniform representation of Agents / Activity / Data interplay • Representation of multi-layered Provenance – eg:the provenance of a workflow run is underpinned by system-level provenance – SONs are suitable for modelling at multiple levels of abstraction IPAW 2012 - P.Missier Expected by-product of the investigation: suggest enhancements to the current SON model 6Thursday, June 21, 2012
10. 10. Talk outline • C-SON: ON + communication relation – a provenance pattern to represent workflow patterns • T-SON: C-SON + temporal abstraction • (more abstraction relations omitted in the talk) • Modelling multi-layered provenance • Agents as evolving systems – provenance of agents IPAW 2012 - P.Missier 7Thursday, June 21, 2012
11. 11. Communication SONs • Goal: to capture communication between ONs that otherwise proceed concurrently • by introducing a Communication relation amongst activities in two ONs – induces a partial order on the states and conditions of the two nets – must result in an acyclic net e1 cannot have happened after f1 e2, f2 must have happened simultaneously IPAW 2012 - P.Missier 8Thursday, June 21, 2012
12. 12. Communication SONs • Goal: to capture communication between ONs that otherwise proceed concurrently • by introducing a Communication relation amongst activities in two ONs – induces a partial order on the states and conditions of the two nets – must result in an acyclic net e1 cannot have happened after f1 e2, f2 must have happened simultaneously IPAW 2012 - P.Missier 8Thursday, June 21, 2012
13. 13. C-SON at work - a first provenance pattern • Each ON models one variable as a system. • The composed activity “A:=A+1; A:=A+B; B:=A+B” is represented as a SON composed of a pair of communicating ONs IPAW 2012 - P.Missier • The resulting SON captures a (partial) order of possible reads and writes leading to the final result 9Thursday, June 21, 2012
14. 14. Workflow execution traces using C-SON X= 10 Y:= f(X) (a) (b) Program Execution specification instance f() <X,Z> := g(X,Y) Y = "200" g() X = 20 Z = "20" 10 r 10 r 10 w 20 X (c) SON representation of Execution trace f g Program execution IPAW 2012 - P.Missier w 20 w 200 r 200 Z Y 10Thursday, June 21, 2012
15. 15. Temporal SON (T-SON) • Goal: to replace part of an ON with new “atomic” actions – a form of temporal abstraction – these new actions only appear atomic at one level of abstraction IPAW 2012 - P.Missier 11Thursday, June 21, 2012
16. 16. T-SON in action: multi-layered provenance • Provenance of computed data naturally comes in layers: – program execution (incl. workflow controller) • system-level primitives, network protocols 10 r 10 t t 10 r 10 t X 10 fetch send 10 X f Program execution get compute t t t f IPAW 2012 - P.Missier Program execution Temporal abstraction used to hide/reveal lower-level details of both 12 systems and their interaction (i.e., reading from storage)Thursday, June 21, 2012
17. 17. T-SON: multi-layered provenance Additional unfolding: - assume f is a service call - reveal details of communication with an underlying service implementation 10 r 10 X f Program execution Service execution IPAW 2012 - P.Missier 13Thursday, June 21, 2012
18. 18. T-SON: multi-layered provenance 10 r 10 t t t msg msg receive send 10 fetch send 10 Service X execution msg msg get receive prep send t t t f IPAW 2012 - P.Missier Program execution 14Thursday, June 21, 2012
19. 19. Agents as evolving systems Alice and Bob collaborate on document editing An agent performs activities that account for changes in the state of the data • F is data (a file) • Data and agents are modelled as systems • Each system is a SON • Communication abstraction used to synchronize events across different IPAW 2012 - P.Missier systems • Bob.draft → F.write, F.read → Alice.”read draft” etc. • For example, Bob in the state b2 is unaware of Alice’s feedback • Bob in state b3 has read Alice’s feedback 15Thursday, June 21, 2012
20. 20. Agents as evolving systems • Tracking the state of agents is important – we know that it is the “version” of Bob that is aware of Alice’s comment that is responsible for the latest edit Below: Bob’s edits to the document do not take account of Alice’s comments ptd draft b2 edit b4 Bob w f1 r f1 w f2 r f2 w f3 IPAW 2012 - P.Missier F read leave a1 a2 draft comments 16 AliceThursday, June 21, 2012
21. 21. Summary • SONs extend well-known Occurrence Nets • Simple graphical notation with formal grounding – amenable to various types of analysis • Appealing for capturing system evolution and inter-system communication • Accommodates multiple levels of abstraction • Evolution traces of Data, Agents and Activities provenance queried seamlessly • Some software tool support (in progress), more work needed here • Feedback for customizations of the SON model itself! IPAW 2012 - P.Missier 17Thursday, June 21, 2012
22. 22. Selected References •  V. Khomenko, M. Koutny, A. Yakovlev: Logic Synthesis for Asynchronous Circuits Based on Petri Net Unfoldings and Incremental SAT. Fundamenta Informaticae 70, 2006. •  http://www.cs.ncl.ac.uk/publications/inproceedings/papers/749.pdf •  M. Koutny, B. Randell: Structured Occurrence Nets: A Formalism for Aiding System Failure Prevention and Analysis Techniques. Fundamenta Informaticae 97, 2009. •  http://www.cs.ncl.ac.uk/publications/trs/papers/1162.pdf •  B. Li, M. Koutny: Verification and Simulation Tool for Communication Structured Occurrence Nets. CS-TR, Newcastle University, (to appear). •  P.M. Merlin and B. Randell: State Restoration in Distributed Systems. Proc. FTCS-8, 1978. •  http://www.cs.ncl.ac.uk/publications/inproceedings/papers/347.pdf •  I. Poliakov, V. Khomenko, A. Yakovlev: Workcraft - A Framework for Interpreted Graph Models. LNCS 5606, 2009. •  B. Randell, M. Koutny: Failures: Their Definition, Modelling and Analysis. LNCS 4711, 2007. •  http://www.cs.ncl.ac.uk/publications/trs/papers/994.pdf IPAW 2012 - P.Missier •  B. Randell, M. Koutny: Structured Occurrence Nets: Incomplete, Contradictory and Uncertain Failure Evidence. CS-TR 1170, Newcastle University, 2009. •  http://www.cs.ncl.ac.uk/publications/trs/papers/1170.pdf 18 Martinique, Jan. 2012 24Thursday, June 21, 2012
23. 23. IPAW 2012 - P.Missier EXTRA material 19Thursday, June 21, 2012
24. 24. SON provenance and PROV read b2 b3 edit b4 feedback Bob (a) f2 r f2 r f2 w f3 F used wasGeneratedBy f2 edit wa f3 (b) sG en era used wasAssociatedWith ted By read wasGeneratedBy feedback Bob_b3 wasDerivedFrom Bob_b4 IPAW 2012 - P.Missier wasAssociatedWith wasDerivedFrom Bob_b2 20Thursday, June 21, 2012
25. 25. T-SON and finite-duration activities In Occurrence Nets, events (activities) are instantaneous. Using temporal abstraction one can add a time duration to activities [s,e] Activity f f with duration [s,e] t t t t t t s e c duration interval of f c t1 t2 tn Time IPAW 2012 - P.Missier 21Thursday, June 21, 2012
26. 26. SON -- behavioural abstraction • Insight: ‘system’ and ‘state’ are not separate concepts • The same graph node may be used to represent either a state or a system, at different levels of abstraction Key idea of Structured Occurrence Nets: • multiple ONs, each portraying a system/state at some level of abstraction IPAW 2012 - P.Missier • associations amongst the ONs are then established by means of new relation types 22Thursday, June 21, 2012
27. 27. B-abstraction in use – An application of behavioural abstraction -- state/system duality – Bob’s state b1 expands into a system’s activities (b1) – the expansion provides additional insight into Bob’s “knowledge level” / “preparedness” prior to drafting the document IPAW 2012 - P.Missier 23 Bob’s state as a systemThursday, June 21, 2012
28. 28. Finding good abstractions - cuts in ON and SON (a) (d) (b) (e) IPAW 2012 - P.Missier (c) 24Thursday, June 21, 2012