bridging the gap between interaction- and process-oriented choreographies
DESCRIPTION
Bridging the gap between Interaction- and Process-Oriented Choreographies. Talk by Ivan Lanese Joint work with Claudio Guidi, Fabrizio Montesi and Gianluigi Zavattaro University of Bologna, Bologna, Italy. Roadmap. IOCs and POCs Different interpretations for IOC Connectedness conditions - PowerPoint PPT PresentationTRANSCRIPT
www.sensoria-ist.eu
Bridging the gap between Interaction-
and Process-Oriented Choreographies
Talk by Ivan LaneseJoint work with Claudio Guidi,
Fabrizio Montesi and Gianluigi ZavattaroUniversity of Bologna, Bologna, Italy
www.sensoria-ist.euRoadmap
IOCs and POCs
Different interpretations for IOC
Connectedness conditions
Bisimilarity results
Conclusions
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www.sensoria-ist.euRoadmap
IOCs and POCs
Different interpretations for IOC
Connectedness conditions
Bisimilarity results
Conclusions
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www.sensoria-ist.euChoreography
Choreography aims at describing the interactions among many participants
Interaction-Oriented Choreography (IOC): obtained by composing basic interactions using composition operators WS-CDL
Process-Oriented Choreography (POC): obtained as the parallel composition of the behavior of different roles BPEL4CHOR, natural extension of orchestration language
BPEL
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a o¡! b
www.sensoria-ist.euFrom design to implementation
IOCs are more easy to understand and to write Good tool for design
POCs are more easily implementable We want to translate automatically a IOC into a POC We project the IOC on the different roles
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www.sensoria-ist.euInteraction-oriented Choreography
Allows to describe interactions from a global point of view
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I ::= a o¡! bj 1 j 0 j I ; I 0 j I k I 0 j I + I 0
(Int er act ion)
a o¡! b ao¡! b¡¡ ¡! 1
(End)
1p
¡! 0
(Sequence)
I ¾¡! I 0 ¾6=p
I ; J ¾¡! I 0; J(Par al l el )
I ¾¡! I 0 ¾6=p
I k J ¾¡! I 0k J
(Choice)
I ¾¡! I 0
I + J ¾¡! I 0
(Seq-end)
Ip
¡! I 0 J ¾¡! J 0
I ; J ¾¡! J 0
(Par -end)
Ip
¡! I 0 Jp
¡! J 0
I k Jp
¡! I 0k J 0
www.sensoria-ist.euProcess-oriented Choreography
Allows to compose the behaviours of different roles Behaviours are based on input/output on operations
We give two semantics to POCs: a synchronous and an asynchronous one
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P ::= o j o j 1 j 0 j P ;P 0 j P j P 0 j P +P 0
S ::= (P )a j S k S0
www.sensoria-ist.euAsynchronous behaviours
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(In)
o o¡! 1(Out )
o o¡! 1
(Async-Out )
hoihoi¡¡! 1
(One)
1p
¡! 0(Sequence)
P °¡! P 0 ° 6=p
P ;Q °¡! P 0;Q
(Inner Par al l el )
P °¡! P 0 ° 6=p
P j Q °¡! P 0 j Q(Choice)
P °¡! P 0
P +Q °¡! P 0
(Seq-end)
Pp
¡! P 0 Q °¡! Q0
P ;Q °¡! Q0
(Inner Par -end)
Pp
¡! P 0 Qp
¡! Q0
P j Qp
¡! P 0 j Q0
www.sensoria-ist.euComposing behaviours
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(Inner )
P °¡! P 0 ° 6= o;p
(P )a° :a¡¡! (P 0)a
(Msg)
P o¡! P 0
(P )ao:a¡¡! (P 0 j hoi)a
(Synchr o)
S hoi :a¡¡ ¡! S0 S00 o:b¡¡! S000
S kS00 ao¡! b¡¡ ¡! S0k S000
(Ext Par al l el )
S °¡! S0
S kS00 °¡! S0kS00
In the synchronous semantics the output is immediately propagated and matched with the input
www.sensoria-ist.euRoadmap
IOCs and POCs
Different interpretations for IOC
Connectedness conditions
Bisimilarity results
Conclusions
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www.sensoria-ist.euOur aim
Given a IOC we want to project it onto roles to get a POC exhibiting the corresponding behaviors
The projection is an homomorphism but for:
We look for connectedness conditions ensuring that such a projection behaves well
The conditions and the meaning of “behaves well” depend on the interpretation of the IOC
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proj(a o¡! b;a) = o
proj(a o¡! b;c) = 1proj(a o¡! b;b) = o
www.sensoria-ist.euWhat ; means?
Consider the simple IOC
In the synchronous case the (atomic) interaction between a and b should occur before the (atomic) interaction between c and d
In the asynchronous case there are different alternatives: Sender: the sending at a should occur before the sending at c Receive: the receive at b should occur before the receive at d Sender-receive: both of the above Disjoint: both the sending at a and the receive at b should
occur before both the sending at c and the receive at d
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a o1¡! b;c o2¡! d
www.sensoria-ist.euA partial order
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Disjoint
Sender Receiver
Sender - receiver
Synchronous
Strincter constraints on IOC
Stronger relation on behaviors
www.sensoria-ist.euRoadmap
IOCs and POCs
Different interpretations for IOC
Connectedness conditions
Bisimilarity results
Conclusions
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www.sensoria-ist.euConnectedness for sequence
Ensures the correctness of sequential composition
Synchronous: {a,b} ∩ {c,d} ≠ Ø Sender: a=c or b=c Receiver: b=c or b=d Disjoint: b=c
The conditions can be generalized to ensure the connectedness of
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a o1¡! b;c o2¡! d
I ; J
www.sensoria-ist.euExample
Consider:
The projection is:
The POC behaves well for synchronous and sender semantics
The POC is not connected for receiver or disjoint semantics
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a o1¡! b;a o2¡! d
(o1;o2)a;(o1)b;(o2)d
www.sensoria-ist.euPoints of choice
Ensures the correctness of choice
Synchronous: The same role should occur in each initial transitions The roles in the two components should be the same
Asynchronous: The sender should be the same The roles in the two components should be the same
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I + J
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If we drop the condition on roles:
In the projection
Interaction on O3 is enabled
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(a o1¡! b+a o2¡! c);b o3¡! c
((o1+o2);1)a k ((o1+1);o3)b k ((o2+1);o3)c
www.sensoria-ist.euCausality-safety
Using many times the same operation may cause problems
For instance a may interact with d
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a o¡! bk c o¡! d
(o)a k (o)b k (o)c k (o)d
www.sensoria-ist.euCausality-safety
We define a causality relation between events of the projected POC e1 < e2 if e2 becomes enabled after e1 has been performed
the exact definition depends on whether the semantics is synchronous or asynchronous
We require causality dependencies between events on the same operation At most one of them can be enabled at the time No interference
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www.sensoria-ist.euRoadmap
IOCs and POCs
Different interpretations for IOC
Connectedness conditions
Bisimilarity results
Conclusions
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www.sensoria-ist.euBisimilarity
We characterize the behavioral relation between a IOC and the projected POC using bisimilarity
Synchronous bisimilarity: IOC transitions are matched by synchronous POC transitions
Sender bisimilarity: IOC transitions are matched by POC sends, POC receives are abstracted away weak w.r.t. POC receive transitions
Receiver bisimilarity: IOC transitions are matched by POC receives, POC sends are abstracted away weak w.r.t. POC send transitions
Disjoint bisimilarity: a IOC transition is matched by subsequent send and receive POC transitions
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www.sensoria-ist.euMain result
If a IOC satisfies all the connectedness conditions for the synchronous/sender/receiver/disjoint semantics then it is synchronous/sender/receiver/disjoint bisimilar to its projection
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www.sensoria-ist.euReceive bisimulation example
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a o1¡! b;c o2¡! b
(o1;1)a k (o1;o2)b k (1;o2)c
(1;1jho1i )a k (o1;o2)b k (1;o2)c
(o1;1)a k (o1;o2)b k (1jho2i )c
(1;1jho1i )a k (o1;o2)b k (1jho2i )c
a o1¡! b
www.sensoria-ist.euReceive bisimulation example
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1;c o2¡! b
(1;1j1)a k (1;o2)b k (1jho2i )c
(1;1j1)a k (1;o2)b k (1;o2)c
c o2¡! b 1
c o2¡! b(1;1j1)a k (1)b k (1j1)c
www.sensoria-ist.euRoadmap
IOCs and POCs
Different interpretations for IOC
Connectedness conditions
Bisimilarity results
Conclusions
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www.sensoria-ist.euExtensions
Internal located actions, recursion and hiding can be added to the language
Value passing can be added A role should own the value to be sent Values can be used to transform nondetermistic choice into
deterministic
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www.sensoria-ist.euBisimulation
Bisimulations and simulations can be defined both for IOCs and for POCs
IOC-POC bisimulation is compatible with those (bi)simulations
The projections of two (bi)similar IOCs are bisimilar One can refine a IOC (e.g., adding auxiliary interactions) and
derive a refined POC Refinement can solve connectedness problems Hiding is necessary to have more powerful refinements
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www.sensoria-ist.euConclusion
We started from the basic question: which is the meaning of a IOC?
We derived different possible interpretations according to the choice of synchronous/asynchronous semantics and to the observable events
For each possibility: We found suitable syntactic conditions ensuring a correct
projection We characterize the behavioral relation between IOC and
POC as a suitable bisimulation relation
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www.sensoria-ist.euRelated work
Carbone, Honda, Yoshida, “Structured communication-centred programming for web services”, ESOP ’07
Honda, Yoshida, Carbone, “Multiparty asynchronous session types”, POPL ’08
Bravetti, Zavattaro, “Towards a unifying theory for choreography conformance and contract compliance”, SC ’07
Busi et al., “Choreography and orchestration conformance for system design”, COORDINATION ’06
Li, Zhu, Pu, “Conformance validation between choreography and orchestration”, TASE ‘07
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www.sensoria-ist.euFuture work
Complete the analysis on a more complex language Recursion/iteration Data Hiding Exceptions
Looking at more complex projection functions Should allow to relax the connectedness conditions
Study the possibility of refinement
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