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Calculi for Committed Choices and Compensations Roberto Bruni - Dipartimento di Informatica, Università di Pisa joint work with Gianluigi Ferrari Hernán.

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1 Calculi for Committed Choices and Compensations Roberto Bruni - Dipartimento di Informatica, Università di Pisa joint work with Gianluigi Ferrari Hernán Melgratti Ugo Montanari Daniele Strollo Emilio Tuosto Dip. Informatica, Univ. Pisa Santa Cruz (CA) USA, 18 January 2005

2 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations2 Motivations Design of business processes rigorous mathematical foundations clean semantics “expressiveness” well-disciplined service composition modular implementation Web Service Composition defining complex services as aggregations of simpler services

3 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations3 Motivations In long lasting negotiations partial agreements can be reached and locally committed by parties To be compensated in case of failure To be published / confirmed on success Formal models are needed To discover specification bugs To reason rigorously To run simulations To ease verification

4 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations4 Compensations To Compensate (Merriam-Webster OnLine) to neutralize the effect of to supply an equivalent to to provide with means of counteracting variation to offset an error, defect, or undesired effect The most important fact: Compensations have a cost

5 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations5 Compensations: Examples Late cancelling of hotel reservations can involve payment of fees Failures on credit checks can cause the abort of parallel activities (which can be partially completed) e.g. to unpackage the goods to be sent to cancel the courier booking Statements of politicians typically require an unbounded number of nested compensations

6 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations6 Approaches Flow Composition or Hierarchical Patterns Similar to workflow systems: a process describes the flow of both control and data among WS Interaction based Composition, Conversational Patterns or Global Model Services describe the ways they can be engaged in a larger process

7 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations7 Flow Composition A1A1 A2A2 A3A3 A4A4 A5A5

8 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations8 Transactional Flows A1A1 A2A2 A3A3 A4A4 A5A5

9 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations9 Compensation A1A1 B1B1 A2A2 B2B2 A3A3 B3B3 A4A4 B4B4 A5A5 B5B5

10 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations10 Compensation Flow A1A1 B1B1 A2A2 B2B2 A3A3 B3B3 A4A4 B4B4 A5A5 B5B5

11 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations11 Nested Flow Diagrams A1A1 B1B1 A2A2 B2B2 A3A3 B3B3 P P A4A4 B4B4

12 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations12 Interaction and Agreements In commercial applications, separately designed and implemented components must interact avoiding ad-hoc proprietary solutions offering alternatives to centralized transaction managers hiding the coordination layer (separation of concerns)

13 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations13 P1P1 P2P2 P3P3 {} Interacting Transactions {}

14 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations14 P1P1 P2P2 P3P3 {} Interacting Transactions {}

15 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations15 P1P1 P2P2 P3P3 {P 3 } {P 2 } Interacting Transactions {}

16 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations16 P1P1 P2P2 P3P3 {P 3 } {P 2 } Interacting Transactions {}

17 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations17 P1P1 P2P2 P3P3 {P 1,P 3 } {P 2 } Interacting Transactions {P 2 }

18 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations18 Outline of the talk Part I Transactional Flows with Compensations Part II A Process Calculus for Distributed Transactions Part III Prototype Implementations

19 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations19 Outline of the talk Part I Transactional Flows with Compensations Part II A Process Calculus for Distributed Transactions Part III Prototype Implementations

20 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations20 Part I - Flows Sequential Sagas Graphical representation Syntax Big Step Semantics Adequacy results Parallel Sagas Nested Sagas Additional features

21 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations21 Flow Diagrams and PDLs Many PDL proposals to describe business processes unambiguously XML-based WSFL, XLANG, BPEL4WS, … Extensions of known calculi committed Join (cJOIN),  t-calculus, web  -calculus Flow-based Structured Activity Compensation (StAC) now evolving to compensating CSP core flow language (FL) for sagas [BMM:POPL2005]

22 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations22 Sequential Sagas: Graphically Accept Order Refuse Order Update Credit Refund Money Prepare Order Update Stock

23 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations23 Sequential Sagas: Syntax Accept Order Refuse Order Update Credit Refund Money Prepare Order Update Stock (Step) X::=0 | A | A % B (Process)P::=X | P;P (Saga)S::={ P }

24 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations24 Sequential Sagas: Syntax Accept Order Refuse Order Update Credit Refund Money Prepare Order Update Stock S = { AO % RO ; UC % RM ; PO % US } (Step) X::=0 | A | A % B (Process)P::=X | P;P (Saga)S::={ P }

25 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations25 Sequential Sagas: Semantics An activity A either commits (A  ) aborts (A  )  = { A 1 ,…, A n  }

26 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations26 Sequential Sagas: Semantics A saga S = { P } under  either commits ( ) aborts ( ) fails ( )  is the observable flow  S        *

27 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations27 A process P under  either commits ( ) aborts ( ) fails ( ) aborts = successfully compensated ß, ß’ are the installed compensations Sequential Sagas: Semantics         *

28 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations28 Sequential Sagas: Semantics (saga)       {P}  

29 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations29 Sequential Sagas: Semantics    0 (zero) (saga)       {P}  

30 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations30 Sequential Sagas: Semantics    0 (zero) (saga)       {P}   A ,    A (s-act)

31 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations31 Sequential Sagas: Semantics A ,    A    0  (zero) (s-act) (s-cmp) (saga) A ,        (f-cmp) A ,         *     {P}  

32 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations32 Sequential Sagas: Semantics (s-step)    ’’    ;’;’ (a-step’)       (a-step’’)       * *

33 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations33 Sequential Sagas: Adequacy  S    and  = A 1 ;…;A n A1A1 AjAj AkAk AnAn

34 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations34 Sequential Sagas: Adequacy  S    and  = A 1 ;…;A n  S    and  = A 1 ;…;A k-1 ;B k-1 ;…;B 1 A1A1 AjAj AkAk AnAn A1A1 AjAj AkAk AnAn BjBj B1B1

35 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations35 Sequential Sagas: Adequacy  S    and  = A 1 ;…;A n  S    and  = A 1 ;…;A k-1 ;B k-1 ;…;B 1  S    and  = A 1 ;…;A k-1 ;B k-1 ;…;B j+1 A1A1 AjAj AkAk AnAn A1A1 AjAj AkAk AnAn BjBj B1B1 A1A1 AjAj AkAk AnAn BjBj B1B1 *

36 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations36 Parallel Sagas: Syntax Accept Order Refuse Order Update Credit Refund Money Prepare Order Update Stock

37 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations37 Parallel Sagas: Syntax (Step) X::=0 | A | A % B (Process)P::=X | P;P | P|P (Saga)S::={ P } Accept Order Refuse Order Update Credit Refund Money Prepare Order Update Stock

38 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations38 Parallel Sagas: Syntax S = { AO % RO ; UC % RM | PO % US } (Step) X::=0 | A | A % B (Process)P::=X | P;P | P|P (Saga)S::={ P } Accept Order Refuse Order Update Credit Refund Money Prepare Order Update Stock

39 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations39 Parallel Sagas: Naïvely B1B1 BjBj BnBn C1C1 CkCk CmCm A1A1 A2A2 B’ 1 B’ j A’ 1 C’ 1 C’ k C’ m A 1 ;(B 1 ;…;B j-1 ;B’ j-1 ;…;B’ 1 | C 1 ;…C m ;C’ m ;…;C’ 1 );A’ 1

40 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations40 Parallel Sagas: Revised A 1 ;(B 1 ;…;B j-1 ;B’ j-1 ;…;B’ 1 | 0);A’ 1 A 1 ;(B 1 ;…;B j-1 ;B’ j-1 ;…;B’ 1 | C 1 ;C’ 1 );A’ 1 … A 1 ;(B 1 ;…;B j-1 ;B’ j-1 ;…;B’ 1 | C 1 ;…C m ;C’ m ;…;C’ 1 );A’ 1 B1B1 BjBj BnBn C1C1 CkCk CmCm A1A1 A2A2 B’ 1 B’ j A’ 1 C’ 1 C’ k C’ m

41 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations41   A process P under  either commits ( ) aborts ( ) fails ( ) is forced to abort ( ) is forced to fail ( )  is the observable concurrent flow     Parallel Sagas: Semantics           * *

42 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations42 Parallel Sagas: Semantics (saga) (forced-abt’)       (forced-abt’’)       *   {,, } *       {P}   

43 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations43   Parallel Sagas: Semantics (s-par)    ’’    |’|’

44 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations44 Parallel Sagas: Semantics    ’’       |  ’;  (c-par’)      1,  2  {, }      * * * * * * * ** **

45 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations45 Parallel Sagas: Semantics (c-par’’)      * * * * * * * ** **    ’’       |  ’;       1,  2  {, } *

46 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations46 Parallel Sagas: Semantics    ’’      |’|’ (f-par)  1  {, }  2  {,,, } * * * *      * * * * * * * ** **

47 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations47 Parallel Sagas: Adequacy Completion

48 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations48 Parallel Sagas: Adequacy Successful Compensation

49 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations49 Parallel Sagas: Adequacy Failed Compensation

50 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations50 Nested Sagas: Graphically Accept Order Refuse Order Update Credit Refund Money Prepare Order Update Stock Add Points Subtract Points

51 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations51 Nested Sagas: Syntax (Step) X::=0 | A | A % B | S (Process)P::=X | P;P | P|P (Saga)S::={ P }

52 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations52 Nested Sagas: Syntax S  { AO % RO ; UC % RM | PO % US | {AP % SP} } Accept Order Refuse Order Update Credit Refund Money Prepare Order Update Stock Add Points Subtract Points

53 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations53 Nested Sagas: Semantics (sub-cmt)       (sub-abt)       (sub-fail)       ß’ acts as default compensation * *

54 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations54 Nested Sagas: Semantics (sub-forced-1) (sub-forced-2’)     *   * (sub-forced-2’’)  {, } *        ;; *      ;;

55 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations55 Nested Sagas: Adequacy Completion

56 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations56 Nested Sagas: Adequacy Successful Compensation

57 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations57 Failed Compensation Nested Sagas: Adequacy

58 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations58 More on Sagas Exception handling try S with P Used to catch crashes during backward computation Forward recovery strategies try S or P Can be used to retry or to improve activities Fully programmable compensations S % P More expressive than default compensation (sub-cmt) Allowed by languages like BPEL4WS Choices: Discriminator P  Q Choices: Internal P  Q Data dependencies A  B Valid executions must satisfy dependency constraints

59 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations59 Outline of the talk Part I Transactional Flows with Compensations Part II A Process Calculus for Distributed Transactions Part III Prototype Implementations

60 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations60 Part II - cJoin Distributed Negotiations CHAM and JOIN cJOIN

61 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations61 Distributed Negotiations Negotiations / Contracts commit, abort, compensation hierarchical decisions dynamic membership fully distributed control Process cooperation coordination / orchestration / choreography different platforms and policies

62 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations62 Our Proposal: cJOIN committed JOIN Process Description Language presentation Non ACID (unrealistic in highly distributed systems) Multiway (several parties can start separately but commit on reached agreement) Programmable abort / non-perfect compensation Concurrency and distribution (Distributed 2PC) Different levels of abstraction (serializability)

63 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations63 Why JOIN? Well-known asynchronous calculus process calculus presentation few constructs, based on rendez-vous (atomic non- local interactions) basis for distributed programming language

64 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations64 Why JOIN? Extends a higher-order functional language parallelism in expressions (fork calls) parallelism in function patterns (join patterns) Distributed implementations JoCaml ( http://join.inria.fr ) http://join.inria.fr Polyphonic C#

65 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations65 Based on an elementary model of concurrency the reflexive chemical abstract machine = generic CHAM + imposing locality + adding reflection locality: only linear reaction patterns allowed each molecule or reaction rule is associated to a single reaction site reflection: reactions can generate new kinds of molecules together with their defining reaction rules Why JOIN?

66 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations66 Chemical Abstract Machine States are called solutions s Multisets of molecules m 1,…,m n data and rules (reflexive CHAM) Hierarchical structure via membranes Group solutions into molecules e.g. { s 1, { s 2 }, { s 3, { s 4 } } } multiset union Evolution (chemical rules) Heating / cooling  (reversible) Structural equivalence Reactions  Transitions Concurrency

67 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations67 JOIN Calculus in One Slide Syntax P,Q::=0 | x  ŷ  | def D in P | P|Q D,E::=J  P | D  E J,K::= x  ŷ  | J|K Operational semantics (CHAM Style) 0  P|Q  P,Q D  E  D,E def D in P  D  dn(D), P  dn(D) ( range  dn(D) “globally fresh”) J  P, J   J  P, P  heating and cooling reaction processes definitions patterns resembles funct. prog. let f(x)=E in F (same scoping discipline)

68 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations68 Join calculus vs.  calculus Join is essentially  with restrictions on communication patterns Join combines restriction, reception and replication in a single receptor definition: they are not available separately Asynchrony forces us to create and send continuations in join Nevertheless, join and asynchronous  have the same expressive power demonstrated by fully abstract encoding in each direction up to weak barbed congruence

69 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations69 Example: Cell Abstraction get  k  | s  v   k  v  | s  v  A cell s contains the value v To get the value: send a message on port get the parameter k is the return address, where the value v will be sent to

70 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations70 Example: Cell Abstraction get  k  | s  v   k  v  | s  v  A cell s contains the value v To set the value: send a message on port set the parameter m is the new value for s k is the return address (for confirmation) set  m,k  | s  v   k  | s  m 

71 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations71 Example: Cell Abstraction get  k  | s  v   k  v  | s  v  The initial value in s is n But get, set and s are locally bound by def get and set must be extruded, otherwise no one can use them instead, s can be kept private set  m,k  | s  v   k  | s  m  def  in s  n 

72 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations72 Example: Cell Abstraction get  k  | s  v   k  v  | s  v  get, set are extruded on public channel c But c should be known only by the owner of the cell… set  m,k  | s  v   k  | s  m  def  in s  n  | c  get,set 

73 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations73 Example: Cell Abstraction get  k  | s  v   k  v  | s  v  A message to create triggers the outermost def: Three fresh names for s, get and set are allocated the initial value of s is the first parameter n get and set are sent back to the second argument c instead s will never be extruded Invariant in every configuration there is exactly one message on s set  m,k  | s  v   k  | s  m  def  in s  n  | c  get,set  def create  n,c   in …

74 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations74 Committed JOIN Syntax M,N::= 0 | x  ŷ  | M|N P,Q ::=M | def D in P | P|Q | abort | [P:Q] D,E ::=J  P | D  E | J  P J,K ::= x  ŷ  | J|K messages programmable abort compensation contract boundaries merge definitions (boards): defined boards must be disjoint from ordinary defined names

75 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations75 Committed JOIN Semantics 0  P|Q  P,Q DEDE  D,E def D in P  D  dn(D), P  dn(D) range(  ) fresh J  P, J   J  P, P 

76 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations76 Committed JOIN Semantics 0  P|Q  P,Q DEDE  D,E def D in P  D  dn(D), P  dn(D) range(  ) fresh J  P, J   J  P, P  [P:Q]  { P,   Q  } compensation is kept frozen contract P can evolve in isolation

77 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations77 Committed JOIN Semantics 0  P|Q  P,Q DEDE  D,E def D in P  D  dn(D), P  dn(D) range(  ) fresh J  P, J   J  P, P  [P:Q]  { P,   Q  } { M|def D in 0,   Q  }  M commit global resources

78 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations78 Committed JOIN Semantics 0  P|Q  P,Q DEDE  D,E def D in P  D  dn(D), P  dn(D) range(  ) fresh J  P, J   J  P, P  [P:Q]  { P,   Q  } { M|def D in 0,   Q  }  M { abort |P,   Q  }  Q compensation on abort

79 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations79 Committed JOIN Semantics 0  P|Q  P,Q DEDE  D,E def D in P  D  dn(D), P  dn(D) range(  ) fresh J  P, J   J  P, P  [P:Q]  { P,   Q  } { M|def D in 0,   Q  }  M { abort |P,   Q  }  Q J 1 |…|J n  P,  i { J i , S i,   Q i  }  J 1 |…|J n  P, {P ,  i S i,   i Q i  } merge n ongoing contracts

80 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations80 JOIN vs cJOIN PROPOSITION cJOIN is a conservative extension of JOIN: P  J Q iff P  cJ Q (for P and Q JOIN processes)

81 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations81 Hotel Booking H  def WaitBooking  [ def request  o   o  $  | price  $   price  $  | confirm  v   BookedRoom  v   price  $   abort in offeringRoom  request,confirm  : Q ]  BookedRoom  v   … in WaitBooking | …

82 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations82 Hotel Booking H  def WaitBooking  [ def request  o   o  $  | price  $   price  $  | confirm  v   BookedRoom  v   price  $   abort in offeringRoom  request,confirm  : Q ]  BookedRoom  v   … in WaitBooking | … C  def BookingHotel  [def hotelMsg  r,c   def offer  $   c  visa  | HotelFound  offer  $   abort in r  offer  in searchRoom  hotelMsg  : Q’ ] in BookingHotel | …

83 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations83 Hotel Booking H  def WaitBooking  [ def request  o   o  $  | price  $   price  $  | confirm  v   BookedRoom  v   price  $   abort in offeringRoom  request,confirm  : Q ]  BookedRoom  v   … in WaitBooking | … C  def BookingHotel  [def hotelMsg  r,c   def offer  $   c  visa  | HotelFound  offer  $   abort in r  offer  in searchRoom  hotelMsg  : Q’ ] in BookingHotel | … HB  def searchRoom  hm  | offeringRoom  r,c   hm  r,c  in H | C

84 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations84 Hotel Booking …, WaitBooking, BookingHotel   …, […, offeringRoom  request,confirm  : Q ], […, searchRoom  hotelMsg  : Q’]  …, […, hotelMsg  request,confirm  : Q | Q’]  …, […, request  offer  : Q | Q’]  …, […, offer  $ , price  $  : Q | Q’]  …, […, confirm  visa , HotelFound, price  $  : Q | Q’]  …, […, BookedRoom  visa , HotelFound : Q | Q’]  …, BookedRoom  visa , HotelFound

85 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations85 Trip Booking I H as before F  def WaitBooking  [ def request  o   o  $  | price  $   price  $  | confirm  v   BookedFlight  v   price  $   abort in offeringFlight  request,confirm  : Q ]  BookedFlight  v   … in WaitBooking | … local name, different from homonym name in H

86 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations86 Trip Booking II C  def hotelOK  fc  | flightOK  hc   fc | hc  BookingHotel  [def hotelMsg  r,c   def offer  $   c  visa  | hotelOK  flightConf   offer  $   abort  flightConf  HotelFound in r  offer  in searchRoom  hotelMsg  : Q’ ]  BookingFlight  [def flightlMsg  r,c   def offer  $   c  visa  | flightOK  hotelConf   offer  $   abort  hotelConf  FlightFound in r  offer  in searchFlight  flightMsg  : Q’’ ] in BookingHotel | BookingFlight | … TB  def searchRoom  hm  | offeringRoom  r,c   hm  r,c   searchFlight  fm  | offeringFlight  r,c   fm  r,c  in H | F | C both needed to commit

87 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations87 Something About cJOIN A simple type system guarantees serializability for Shallow processes Proof via correspondence w.r.t. big step semantics Commit primitives of cJOIN can be used to implement committed choices of AKL explicit encoding of search strategies and unification via continuation passing and compensation Zero-safe nets can also be straightforwardly encoded as cJOIN processes

88 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations88 Outline of the talk Part I Transactional Flows with Compensations Part II A Process Calculus for Distributed Transactions Part III Prototype Implementations

89 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations89 Java Transactional Web Services (JTWS) Java Signal Core Layer (JSCL) Java Transactional Layer (JTL) cJOIN compiler D2PC Part III - Implementation

90 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations90 JTWS Methodology GOAL: Automatic generation of the “coordination code” from a description of a composed WS design as well-formed flow diagrams or as processes in a suitable language automatic generation of coordination wrappers for invoking involved services in a sound way for managing commitments and compensations

91 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations91 JTWS and JSCL JTWS tailored to long running transactions JTWS is based on signal exchanges, publish/subscribe, event notification JSCL gives a minimal set of functionalities for creation/dismissal of new signal types signal emitters / handlers as services describing connections between components asynchronous / synchronous typed, peer-to-peer, unidirectional broadcast and bidirectional just requires additional links management of flow sessions

92 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations92 JTL Specialized kind of JTWS component API for (paradigms of) connectors only a minimal subset of signals is considered three signals can encode compensable transactions onInvoke onRollBack onCommit

93 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations93 JTL Component Wrappers WS iRb In iCt Out oRb oCt

94 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations94 JTL Transactional Component WS1 iRb In iCt Out oRb oCt WS2 WS1 % WS2 links are dynamically established depending on the internal state

95 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations95 JTL Sequence InOut iRb iCt oRb oCt JTL1 ; JTL2

96 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations96 JTL Transactional Sequence InOut offer the method addInternalComponent { JTL1 ; JTL2 }

97 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations97 JTL Trans. Parallel Component InOut offer the method addInternalComponent { JTL1 | JTL2 }

98 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations98 Encoding of cJOIN in JOIN Aim: Define an implementation of cJOIN in JOIN Associate to every cJOIN process a JOIN process that simulate its behavior Ideas: Identification of basic forms for definitions Definition of a type system to single out canonical processes Reuse controllers of the D2PC protocol

99 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations99 Distributed 2PC (D2PC) The Distributed 2PC is a variant of the decentralized 2PC When a participant P is ready to commit it has only a partial knowledge of the whole set of participants Only those who directly cooperated with P To commit P must contact all its neighbors and learn the identity of other participants from them The D2PC can be conveniently written in Jocaml

100 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations100 D2PC Every participant P acts as coordinator During the transaction P builds its own synchronization set L P of cooperating agents When P is ready to commit, P asks readiness to processes in L P (if empty P was isolated and can commit) In doing so, P sends them the set L P Other participants will send to P either a successful reply with their own synchronization sets or a failure message (in this case, failure is then propagated) Successful replies are added to L P The protocol terminates when L P is transitively closed

101 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations101 P1P1 P2P2 P3P3 Example: D2PC

102 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations102 P1P1 P2P2 P3P3 {} Example: D2PC

103 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations103 P1P1 P2P2 P3P3 {} Example: D2PC

104 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations104 P1P1 P2P2 P3P3 {} Example: D2PC {}

105 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations105 P1P1 P2P2 P3P3 {} Example: D2PC {}

106 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations106 P1P1 P2P2 P3P3 {P 3 } {P 2 } Example: D2PC {}

107 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations107 P1P1 P2P2 P3P3 {P 3 } {P 2 } Example: D2PC {}

108 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations108 P1P1 P2P2 P3P3 {P 1,P 3 } {P 2 } Example: D2PC {P 2 }

109 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations109 P1P1 P2P2 P3P3 {P 1,P 3 } {P 2 } Example: D2PC {P 2 }

110 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations110 P1P1 P2P2 P3P3 {P 1,P 3 } {P 2 } [P 2 ] () Example: D2PC {P 2 }

111 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations111 P1P1 P2P2 P3P3 {P 1,P 3 } {P 2 } [P 2 ] () Example: D2PC {P 2 }

112 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations112 P1P1 P2P2 P3P3 {P 1,P 3 } [P 1,P 3 ] () {P 2 } [P 2 ] () Example: D2PC {P 2 }

113 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations113 P1P1 P2P2 P3P3 {P 2 } [P 2 ] () {P 1,P 3 } [P 1,P 3 ] () Example: D2PC {P 2 }

114 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations114 P1P1 P2P2 P3P3 {P 2 } [P 2 ] () {P 1,P 3 } [P 1,P 3 ] (P 3 ) Example: D2PC {P 2 }

115 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations115 P1P1 P2P2 P3P3 {P 1,P 2 } [P 2 ] (P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 3 ) Example: D2PC {P 2 }

116 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations116 P1P1 P2P2 P3P3 {P 1,P 2 } [P 1,P 2 ] (P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 3 ) Example: D2PC {P 2 }

117 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations117 P1P1 P2P2 P3P3 {P 1,P 2 } [P 1,P 2 ] (P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 3 ) Example: D2PC {P 2 }

118 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations118 P1P1 P2P2 P3P3 {P 2 } [P 2 ] () {P 1,P 2 } [P 1,P 2 ] (P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 3 ) Example: D2PC

119 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations119 P1P1 P2P2 P3P3 {P 2 } [P 2 ] () {P 1,P 2 } [P 1,P 2 ] (P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 3 ) Example: D2PC

120 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations120 P1P1 P2P2 P3P3 {P 2 } [P 2 ] () {P 1,P 2 } [P 1,P 2 ] (P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 1,P 3 ) Example: D2PC

121 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations121 P1P1 Q2Q2 P3P3 {P 2 } [P 2 ] () {P 1,P 2 } [P 1,P 2 ] (P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 1,P 3 ) Example: D2PC

122 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations122 P1P1 Q2Q2 P3P3 {P 2,P 3 } [P 2 ] (P 2 ) {P 1,P 2 } [P 1,P 2 ] (P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 1,P 3 ) Example: D2PC

123 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations123 P1P1 Q2Q2 P3P3 {P 2,P 3 } [P 2 ] (P 2 ) {P 1,P 2 } [P 1,P 2 ] (P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 1,P 3 ) Example: D2PC

124 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations124 P1P1 Q2Q2 P3P3 {P 2,P 3 } [P 2 ] (P 2 ) {P 1,P 2 } [P 1,P 2 ] (P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 1,P 3 ) Example: D2PC

125 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations125 P1P1 Q2Q2 P3P3 {P 2,P 3 } [P 2,P 3 ] (P 2,P 3 ) {P 1,P 2 } [P 1,P 2 ] (P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 1,P 3 ) Example: D2PC

126 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations126 P1P1 Q2Q2 P3P3 {P 2,P 3 } [P 2,P 3 ] (P 2,P 3 ) {P 1,P 2 } [P 1,P 2 ] (P 1,P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 1,P 3 ) Example: D2PC

127 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations127 Q1Q1 Q2Q2 Q3Q3 {P 2,P 3 } [P 2,P 3 ] (P 2,P 3 ) {P 1,P 2 } [P 1,P 2 ] (P 1,P 2 ) {P 1,P 3 } [P 1,P 3 ] (P 1,P 3 ) Example: D2PC

128 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations128 Final Remarks I Our definition for compensable flow languages abstracts away from low-level computations can be easily extended independent from the coordination mechanisms that implement the primitives Java Transactional Web Services (JTWS) Distributed implementation of flows Allows to reason about program properties Adequacy Correctness of implementation

129 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations129 Final Remarks II cJOIN models multi-way transactions by describing interacting agents but not their global structure Shallow cJOIN is serializable cJOIN primitives are implementable in a distributed way at least the subcalculus of flat processes D2PC protocol is used

130 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations130 Some Pointers R. Bruni, C. Laneve, U. Montanari CONCUR 2002 (D2PC) R. Bruni, H. Melgratti, U. Montanari POPL 2005 (Flows) IFIP TCS 2004 + COMETA 2003 (cJOIN) Hernán Melgratti PhD Thesis submitted (Flows, cJOIN and more) Daniele Strollo Master Thesis in preparation (JTWS)

131 Roberto Bruni @ Santa Cruz (CA) USA 18 Jan. 2005 Calculi for Committed Choices and Compensations131 JOIN: An Example A process P P  z  x,z  | def x  y   z  y,x  in x  v  P as a solution { z  x,z , w  y   z  y,w , w  v  } A reaction { z  x,z , w  y   z  y,w , w  v  }  { z  x,z , w  y   z  y,w , z  v,w  } bound name extrusion defined name received name free name  -conversion

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