Forward Chaining in HALO

1. Forward Chaining in HALO An Implementation Strategy for History-based Logic Pointcuts @International Conference On Dynamic Languages 2007, Lugano, August 27th, 2007 Charlotte Herzeel, Kris Gybels, Pascal Costanza, Coen De Roover and Theo D’hondt Programming Technology Laboratory Vrije Universiteit Brussel

2. Overview • Introduction • Logic Meta Programming & Aspect-Oriented Programming • Running example - going shopping • History-based Aspects using LOgic: • Aspect-Oriented Programming for Lisp • meta model = the program execution • hybrid language (temporal logic programming/CLOS) • Implementing HALO • HALO weaver Architecture • Query Engine based on RETE • Reducing Memory Overhead

3. Scattering & tangling

4. Scattering & tangling Tyranny of the dominant decomposition

5. Scattering & tangling Tyranny of the dominant decomposition tangling & scattering -- maintainability -- reusability -- readability !

6. Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) tangling & scattering -- maintainability -- reusability -- readability !

7. Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) tangling & scattering -- maintainability -- reusability -- readability !

8. Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability !

9. CLOS: before, after, around Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability !

10. CLOS: before, after, around Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability ! (defmethod shareAccount :around ((c client), (a account)) (log “sharing account ~s ~s” c a) (call-next-method)) (defmethod withdraw :around ((c client), (i integer)) ...) (defmethod credit :around ((c client), (i integer)) ...)

11. CLOS: before, after, around Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability !

12. CLOS: before, after, around Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability ! Aspect-Oriented Programming

13. CLOS: before, after, around Aspect Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability ! Aspect-Oriented Programming

14. CLOS: before, after, around Aspect Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability ! Aspect-Oriented Programming “at each sensitive method call,

15. CLOS: before, after, around Aspect Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability ! Aspect-Oriented Programming make a log entry” “at each sensitive method call,

16. CLOS: before, after, around Aspect Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability ! Aspect-Oriented Programming pointcut make a log entry” “at each sensitive method call,

17. CLOS: before, after, around Aspect Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability ! Aspect-Oriented Programming pointcut make a log entry” advice “at each sensitive method call,

18. CLOS: before, after, around Aspect Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability ! Aspect-Oriented Programming pointcut make a log entry” advice “at each sensitive method call, (defmethod shareAccount :around ((c client), (a account)) (log “sharing account ~s ~s” c a) (call-next-method)) (defmethod withdraw :around ((c client), (i integer)) ...) (defmethod credit :around ((c client), (i integer)) ...)

19. CLOS: before, after, around Aspect Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability ! Aspect-Oriented Programming pointcut make a log entry” advice “at each sensitive method call,

20. CLOS: before, after, around Aspect Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability ! ?macros Aspect-Oriented Programming pointcut make a log entry” advice “at each sensitive method call,

21. CLOS: before, after, around Aspect Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability ! -- current join point only ?macros Aspect-Oriented Programming pointcut make a log entry” advice “at each sensitive method call,

22. CLOS: before, after, around Aspect Scattering & tangling Tyranny of the dominant decomposition Bank Client Account withdraw(AccountNr, Integer) credit(AccountNr, Integer) view(AccountNr) 1 * * * register(Client) createAccount(Client) shareAccount(Client, Account) login(Client) logout(Client) withdraw(Client, Integer) credit(Client, Integer) transfer(Client, Account) view(Client) log sensitive operations = crosscutting concern tangling & scattering -- maintainability -- reusability -- readability ! -- current join point only ?macros ! history of join points Aspect-Oriented Programming pointcut make a log entry” advice “at each sensitive method call,

23. Declarative Meta Programming & Aspect-Oriented Programming base)

24. Declarative Meta Programming & Aspect-Oriented Programming (base base)

25. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base))

26. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language meta model MP

27. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model

28. Declarative Meta Programming & Aspect-Oriented Programming SOUL for DMP: Base code to facts -> Image querying Symbiosis (quasiquoting) Rule abstraction (Libraries) Generating code Detecting/Verifying coding patterns (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model

29. Declarative Meta Programming & Aspect-Oriented Programming (defclass account () ((balance))) (defclass client () ((id))) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) SOUL for DMP: Base code to facts -> Image querying Symbiosis (quasiquoting) Rule abstraction (Libraries) Generating code Detecting/Verifying coding patterns (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model

30. Declarative Meta Programming & Aspect-Oriented Programming (defclass account () ((balance))) (defclass client () ((id))) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) SOUL for DMP: Base code to facts -> Image querying Symbiosis (quasiquoting) Rule abstraction (Libraries) Generating code Detecting/Verifying coding patterns (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model

31. Declarative Meta Programming & Aspect-Oriented Programming (defclass account () ((balance))) (defclass client () ((id))) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) class( account , <account>) classImplementsMethodNamed (<account> , withdraw, <withdraw>) method(<account>, <withdraw>) methodName(<withdraw>, withdraw) methodArguments(<withdraw>, ()) methodStatements(<withdraw>, ((setf (balance a) (- (balance a) nr)))) ... SOUL for DMP: Base code to facts -> Image querying Symbiosis (quasiquoting) Rule abstraction (Libraries) Generating code Detecting/Verifying coding patterns (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model

32. Declarative Meta Programming & Aspect-Oriented Programming (defclass account () ((balance))) (defclass client () ((id))) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) class( account , <account>) classImplementsMethodNamed (<account> , withdraw, <withdraw>) method(<account>, <withdraw>) methodName(<withdraw>, withdraw) methodArguments(<withdraw>, ()) methodStatements(<withdraw>, ((setf (balance a) (- (balance a) nr)))) ... abstractClassHeuristic() if forall(abstractClass(?C),baseClass(?C)), forall(baseClass(?C),abstractClass(?C)). SOUL for DMP: Base code to facts -> Image querying Symbiosis (quasiquoting) Rule abstraction (Libraries) Generating code Detecting/Verifying coding patterns (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model

33. Declarative Meta Programming & Aspect-Oriented Programming (defclass account () ((balance))) (defclass client () ((id))) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) class( account , <account>) classImplementsMethodNamed (<account> , withdraw, <withdraw>) method(<account>, <withdraw>) methodName(<withdraw>, withdraw) methodArguments(<withdraw>, ()) methodStatements(<withdraw>, ((setf (balance a) (- (balance a) nr)))) ... abstractClassHeuristic() if forall(abstractClass(?C),baseClass(?C)), forall(baseClass(?C),abstractClass(?C)). SOUL for DMP: Base code to facts -> Image querying Symbiosis (quasiquoting) Rule abstraction (Libraries) Generating code Detecting/Verifying coding patterns (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model compute

34. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model

35. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model CARMA: AOP with a SOUL modularizing scattered & tangled code Join point type predicates Link to shadows Symbiosis Loose coupling aspect/base Pattern-based pointcuts

36. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model (defclass account () ...) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) (withdraw *account* 3) (print (get-value *account* balance)) CARMA: AOP with a SOUL modularizing scattered & tangled code Join point type predicates Link to shadows Symbiosis Loose coupling aspect/base Pattern-based pointcuts

37. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model (defclass account () ...) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) (withdraw *account* 3) (print (get-value *account* balance)) CARMA: AOP with a SOUL modularizing scattered & tangled code Join point type predicates Link to shadows Symbiosis Loose coupling aspect/base Pattern-based pointcuts

38. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model class( account , <account>) classImplementsMethodNamed (<account> , withdraw, <withdraw>) send(<jp>, withdraw, [<account>]) assignment(<jp>, balance, 10, 7) reference(<jp2>, balance, 7) 1. 2. (defclass account () ...) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) (withdraw *account* 3) (print (get-value *account* balance)) CARMA: AOP with a SOUL modularizing scattered & tangled code Join point type predicates Link to shadows Symbiosis Loose coupling aspect/base Pattern-based pointcuts

39. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model class( account , <account>) classImplementsMethodNamed (<account> , withdraw, <withdraw>) send(<jp>, withdraw, [<account>]) assignment(<jp>, balance, 10, 7) reference(<jp2>, balance, 7) 1. 2. (defclass account () ...) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) (withdraw *account* 3) (print (get-value *account* balance)) CARMA: AOP with a SOUL modularizing scattered & tangled code Join point type predicates Link to shadows Symbiosis Loose coupling aspect/base Pattern-based pointcuts carma pointcut

40. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model rule abstraction, unification, recursion class( account , <account>) classImplementsMethodNamed (<account> , withdraw, <withdraw>) send(<jp>, withdraw, [<account>]) assignment(<jp>, balance, 10, 7) reference(<jp2>, balance, 7) 1. 2. (defclass account () ...) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) (withdraw *account* 3) (print (get-value *account* balance)) CARMA: AOP with a SOUL modularizing scattered & tangled code Join point type predicates Link to shadows Symbiosis Loose coupling aspect/base Pattern-based pointcuts carma pointcut

41. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model rule abstraction, unification, recursion class( account , <account>) classImplementsMethodNamed (<account> , withdraw, <withdraw>) send(<jp>, withdraw, [<account>]) assignment(<jp>, balance, 10, 7) reference(<jp2>, balance, 7) 1. 2. (defclass account () ...) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) (withdraw *account* 3) (print (get-value *account* balance)) reusability, reasoning CARMA: AOP with a SOUL modularizing scattered & tangled code Join point type predicates Link to shadows Symbiosis Loose coupling aspect/base Pattern-based pointcuts carma pointcut

42. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model rule abstraction, unification, recursion class( account , <account>) classImplementsMethodNamed (<account> , withdraw, <withdraw>) send(<jp>, withdraw, [<account>]) assignment(<jp>, balance, 10, 7) reference(<jp2>, balance, 7) 1. 2. (defclass account () ...) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) (withdraw *account* 3) (print (get-value *account* balance)) reusability, reasoning

43. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model rule abstraction, unification, recursion class( account , <account>) classImplementsMethodNamed (<account> , withdraw, <withdraw>) send(<jp>, withdraw, [<account>]) assignment(<jp>, balance, 10, 7) reference(<jp2>, balance, 7) 1. 2. (defclass account () ...) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) (withdraw *account* 3) (print (get-value *account* balance)) reusability, reasoning HALO: AOP with a memory Temporal/Stateful pointcuts

44. Declarative Meta Programming & Aspect-Oriented Programming (base base)(meta base)) meta language object language pointcut language meta model base language MP AOP jp model rule abstraction, unification, recursion class( account , <account>) classImplementsMethodNamed (<account> , withdraw, <withdraw>) send(<jp>, withdraw, [<account>]) assignment(<jp>, balance, 10, 7) reference(<jp2>, balance, 7) 1. 2. (defclass account () ...) (defmethod withdraw ((a account) nr) (setf (balance a) (- (balance a) nr))) (defmethod credit ((a account) nr) ...) (withdraw *account* 3) (print (get-value *account* balance)) reusability, reasoning HALO: AOP with a memory Temporal/Stateful pointcuts record

45. VISAMasterCardMasterCard Boutique Clothing Running example

49. VISAMasterCardMasterCard Boutique Clothing -10% Running example

56. VISAMasterCardMasterCard $ Boutique Clothing Running example

57. VISAMasterCardMasterCard $ Boutique Clothing Running example

58. VISAMasterCardMasterCard $ Boutique Clothing Running example 1 * Shop Article Basket login(shop,name,pwd) buy(shop,name,pwd) checkout() current-rate(article) set-rate(article, rate) 1 1 1 * * * * 1 Basket User Promotions

61. VISAMasterCardMasterCard $ Boutique Clothing Running example 1 * Shop Article Basket login(shop,name,pwd) buy(shop,name,pwd) checkout() current-rate(article) set-rate(article, rate) 1 1 1 * * * * 1 Basket User Promotions Stateful!!

62. Mental Model fact generator query engine jp ctr (defclass user () ((name)) (defmethod checkout ((u user)) ...) (defmethod buy ((u user) (a article)) ...) base most-recent, all-past, since, cflow temporal relations (at ((gf-call checkout ?u) (most-recent (buy ?u ?a))) (log user ~s bought ~s ?u ?a)) aspect (defrule (buy ?u) (gf-call buy ?u ?a)) rules TN: (gf-call checkout <user>) TN-1: (gf-call buy <user> <cd>) jp facts

63. Join Point Model (make-instance user) (create user <kris>) (checkout <kris>) (gf-call checkout <kris>) (end-gf-call checkout <kris> nil) (get-value <kris> name) (slot-get <kris> name kris ) (setf (get-value <kris> name) kris ) (slot-set <kris> name kris ) CLOS Join Point Facts

64. Join Point Model (make-instance user) (create user <kris>) (checkout <kris>) (gf-call checkout <kris>) (end-gf-call checkout <kris> nil) (get-value <kris> name) (slot-get <kris> name kris ) (setf (get-value <kris> name) kris ) (slot-set <kris> name kris ) CLOS Join Point Facts ?obj Join Point Type Predicates ?obj ?name ?val ?oval?obj ?name ?val ?obj?gf-name ?gf-name ?obj ?res

65. Join Point Model (make-instance user) (create user <kris>) (checkout <kris>) (gf-call checkout <kris>) (end-gf-call checkout <kris> nil) (get-value <kris> name) (slot-get <kris> name kris ) (setf (get-value <kris> name) kris ) (slot-set <kris> name kris ) CLOS Join Point Facts ?obj Join Point Type Predicates ?obj ?name ?val ?oval?obj ?name ?val ?obj?gf-name ?gf-name ?obj ?res Extensible ... (defrule (promotion “25-12-2008”))

66. Join Point Model (make-instance user) (create user <kris>) (checkout <kris>) (gf-call checkout <kris>) (end-gf-call checkout <kris> nil) (get-value <kris> name) (slot-get <kris> name kris ) (setf (get-value <kris> name) kris ) (slot-set <kris> name kris ) CLOS Join Point Facts Hybrid Pointcuts ?obj Join Point Type Predicates ?obj ?name ?val ?oval?obj ?name ?val ?obj?gf-name ?gf-name ?obj ?res (escape ?name (password ?user)) Extensible ... (defrule (promotion “25-12-2008”)) (defrule (date ?date) (escape ?date (get-current-time)))

67. Join Point Model (make-instance user) (create user <kris>) (checkout <kris>) (gf-call checkout <kris>) (end-gf-call checkout <kris> nil) (get-value <kris> name) (slot-get <kris> name kris ) (setf (get-value <kris> name) kris ) (slot-set <kris> name kris ) CLOS Join Point Facts Hybrid Pointcuts ?obj Join Point Type Predicates ?obj ?name ?val ?oval?obj ?name ?val ?obj?gf-name ?gf-name ?obj ?res (escape ?name (password ?user)) Extensible ... (defrule (promotion “25-12-2008”)) (defrule (date ?date) (escape ?date (get-current-time)))

68. Join Point Model (make-instance user) (create user <kris>) (checkout <kris>) (gf-call checkout <kris>) (end-gf-call checkout <kris> nil) (get-value <kris> name) (slot-get <kris> name kris ) (setf (get-value <kris> name) kris ) (slot-set <kris> name kris ) CLOS Join Point Facts Hybrid Pointcuts ?obj Join Point Type Predicates ?obj ?name ?val ?oval?obj ?name ?val ?obj?gf-name ?gf-name ?obj ?res (escape ?name (password ?user)) Extensible ... (defrule (promotion “25-12-2008”)) (defrule (date ?date) (escape ?date (get-current-time))) Ad-hoc context-exposure

69. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>)

70. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer

71. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer 1.

72. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer login 1.

73. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer login 2. 1.

74. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer login buy 2. 1.

75. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer login buy 2. 3. 1.

76. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer logoutlogin buy 2. 3. 1.

77. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer logoutlogin buy 2. 3. 4. 1.

78. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer loginlogoutlogin buy 2. 3. 4. 1.

79. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer loginlogoutlogin buy 2. 3. 4. 1. 5.

80. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer login buylogoutlogin buy 2. 3. 4. 1. 5.

81. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer login buylogoutlogin buy 2. 3. 4. 1. 5. 6.

82. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer login buy buylogoutlogin buy 2. 3. 4. 1. 5. 6.

83. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer login buy buylogoutlogin buy 2. 3. 4. 1. 5. 6. 7.

84. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) T customer login buy checkoutbuylogoutlogin buy 2. 3. 4. 1. 5. 6. 7.

85. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) ((gf-call checkout ?args) (most-recent (gf-call buy ?args2))) T customer login buy checkoutbuylogoutlogin buy 2. 3. 4. 1. 5. 6. 7.

88. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) ((gf-call checkout ?args) (most-recent (gf-call buy ?args2))) T customer login buy buy checkoutbuy logoutlogin T customer login buy checkoutbuylogoutlogin buy 2. 3. 4. 1. 5. 6. 7.

89. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) ((gf-call checkout ?args) (all-past (gf-call buy ?args2))) ((gf-call checkout ?args) (most-recent (gf-call buy ?args2))) T customer login buy buy checkoutbuy logoutlogin T customer login buy checkoutbuylogoutlogin buy 2. 3. 4. 1. 5. 6. 7.

94. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) ((gf-call checkout ?args) (all-past (gf-call buy ?args2))) ((gf-call checkout ?args) (most-recent (gf-call buy ?args2))) T customer login buy buy checkoutbuy logoutlogin T customer login buy checkoutbuylogoutlogin buy T customer login buy buy checkoutbuy logoutlogin 2. 3. 4. 1. 5. 6. 7.

95. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) ((gf-call checkout ?args) (all-past (gf-call buy ?args2))) ((gf-call checkout ?args) (most-recent (gf-call buy ?args2))) T customer login buy buy checkoutbuy logoutlogin T customer login buy checkoutbuylogoutlogin buy T customer login buy buy checkoutbuy logoutlogin ((gf-call checkout ?args) (since (most-recent (gf-call login ?args2)) (all-past (gf-call buy ?args3) 2. 3. 4. 1. 5. 6. 7.

100. Temporal Matching (login <shop> <kris> kris kros ) (buy <kris> <jacket>) (logout <kris>) (login <shop> <kris> kris kros ) (buy <kris> <t-shirt>) (buy <kris> <socks>) (checkout <kris>) ((gf-call checkout ?args) (all-past (gf-call buy ?args2))) ((gf-call checkout ?args) (most-recent (gf-call buy ?args2))) T customer login buy buy checkoutbuy logoutlogin T customer login buy checkoutbuylogoutlogin buy T customer login buy buy checkoutbuy logoutlogin ((gf-call checkout ?args) (since (most-recent (gf-call login ?args2)) (all-past (gf-call buy ?args3) Stateful context-exposure 2. 3. 4. 1. 5. 6. 7.

101. Stateful context-exposure (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>)))

102. Stateful context-exposure (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) T <kris>

103. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) T <kris>

104. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 1. T <kris>

105. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 1. T <kris>

106. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 1. T <kris>

107. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 1. T <kris> login

108. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. T <kris> login

109. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. T <kris> login buy

110. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. T <kris> login buy

111. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. 6. T <kris> login buy

112. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. 6. T <kris> buylogin buy

118. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (defrule (rate-for ?rate ?article) (escape ?promo (singleton-instance promotions) (escape ?rate (discount-rate-for ?promo ?article))) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. 6. T <kris> buylogin buy

122. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. 6. T <kris> buylogin buy “<kris> gets a 0.05% discount on <cd>”

123. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. 6. T <kris> buylogin buy “<kris> gets a 0.05% discount on <cd>”

124. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. 6. T <kris> buylogin buy “<kris> gets a 0.05% discount on <cd>” “<kris> gets a 0.05% discount on <cd>”

125. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. 6. T <kris> buylogin buy “<kris> gets a 0.05% discount on <cd>” “<kris> gets a 0.05% discount on <cd>”

126. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (at ((gf-call buy ?user ?article) (rate-for ?rate ?article) (most-recent (gf-call login ?user _ _ _))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. 6. T <kris> buylogin buy “<kris> gets a 0.05% discount on <cd>” “<kris> gets a 0.05% discount on <cd>”

129. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (at ((gf-call buy ?user ?article) (rate-for ?rate ?article) (most-recent (gf-call login ?user _ _ _))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. 6. T <kris> buylogin buy “<kris> gets a 0.05% discount on <cd>” “<kris> gets a 0.05% discount on <cd>” <kris> gets a 0.05% discount on <cd>

130. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (at ((gf-call buy ?user ?article) (rate-for ?rate ?article) (most-recent (gf-call login ?user _ _ _))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. 6. T <kris> buylogin buy “<kris> gets a 0.05% discount on <cd>” “<kris> gets a 0.05% discount on <cd>” <kris> gets a 0.05% discount on <cd>

131. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (at ((gf-call buy ?user ?article) (rate-for ?rate ?article) (most-recent (gf-call login ?user _ _ _))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. 6. T <kris> buylogin buy “<kris> gets a 0.05% discount on <cd>” “<kris> gets a 0.05% discount on <cd>” <kris> gets a 0.05% discount on <cd> <kris> gets a 0.00% discount on <cd>

132. Stateful context-exposure (at ((gf-call buy ?user ?article) (most-recent (gf-call login ?user _ _ _) (rate-for ?rate ?article))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (at ((gf-call buy ?user ?article) (rate-for ?rate ?article) (most-recent (gf-call login ?user _ _ _))) (format t ~s gets a ~s % discount on ~s ?user ?rate ?article)) (let ((promo (singleton-instance promotions))) (setf (rate-for promo) <cd> 0.05) (login <kris> <shop> kris kros ) (buy <kris> <cd>) (setf (rate-for promo) <cd> 0.00) (buy <kris> <cd>))) 2. 3. 4. 1. 5. 6. T <kris> buylogin buy “<kris> gets a 0.05% discount on <cd>” “<kris> gets a 0.05% discount on <cd>” <kris> gets a 0.05% discount on <cd> <kris> gets a 0.00% discount on <cd> Stateful context-exposure

133. Weaver Implementation fact generator query engine jp ctr (defclass user () ((name)) (defmethod checkout ((u user)) ...) (defmethod buy ((u user) (a article)) ...) base most-recent, all-past, since, cflow temporal relations (at ((gf-call checkout ?u) (most-recent (buy ?u ?a))) (log user ~s bought ~s ?u ?a)) aspect (defrule (buy ?u) (gf-call buy ?u ?a)) rules TN: (gf-call checkout <user>) TN-1: (gf-call buy <user> <cd>) fact base

135. Weaver Implementation fact generator query engine jp ctr (defclass user () ((name)) (defmethod checkout ((u user)) ...) (defmethod buy ((u user) (a article)) ...) base most-recent, all-past, since, cflow temporal relations (at ((gf-call checkout ?u) (most-recent (buy ?u ?a))) (log user ~s bought ~s ?u ?a)) aspect (defrule (buy ?u) (gf-call buy ?u ?a)) rules TN: (gf-call checkout <user>) TN-1: (gf-call buy <user> <cd>) fact base * by wrapping class & generic function protocols in CLOS MOP * explicit meta class tagging

138. Weaver Implementation fact generator query engine jp ctr (defclass user () ((name)) (defmethod checkout ((u user)) ...) (defmethod buy ((u user) (a article)) ...) base most-recent, all-past, since, cflow temporal relations (at ((gf-call checkout ?u) (most-recent (buy ?u ?a))) (log user ~s bought ~s ?u ?a)) aspect (defrule (buy ?u) (gf-call buy ?u ?a)) rules TN: (gf-call checkout <user>) TN-1: (gf-call buy <user> <cd>) fact base * extension of RETE forward chaining, supporting temporal operators + hybrid pointcuts * copy semantics through static analysis

141. Weaver Implementation fact generator query engine jp ctr (defclass user () ((name)) (defmethod checkout ((u user)) ...) (defmethod buy ((u user) (a article)) ...) base most-recent, all-past, since, cflow temporal relations (at ((gf-call checkout ?u) (most-recent (buy ?u ?a))) (log user ~s bought ~s ?u ?a)) aspect (defrule (buy ?u) (gf-call buy ?u ?a)) rules TN: (gf-call checkout <user>) TN-1: (gf-call buy <user> <cd>) fact base * reducing the join point history dynamically * gbc in RETE based on semantics of temporal operators * results presented @ RV 2007

142. Backward Chaining vs Rete Forward Chaining (at ((gf-call checkout (?user)) (most-recent (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)))) (discount ?user ?rate))

143. Backward Chaining vs Rete Forward Chaining (at ((gf-call checkout (?user)) (most-recent (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)))) (discount ?user ?rate)) (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate)query engine

144. Backward Chaining Backward Chaining vs Rete Forward Chaining (at ((gf-call checkout (?user)) (most-recent (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)))) (discount ?user ?rate)) (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine

157. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine

158. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine ’’On every checkout, give a discount based on the rate at login time’’

159. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) ’’On every checkout, give a discount based on the rate at login time’’

160. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) 1. ’’On every checkout, give a discount based on the rate at login time’’

161. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05)1. ’’On every checkout, give a discount based on the rate at login time’’

168. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05)1. 2. ’’On every checkout, give a discount based on the rate at login time’’

169. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) 1. 2. ’’On every checkout, give a discount based on the rate at login time’’

176. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) 1. 2. 3. ’’On every checkout, give a discount based on the rate at login time’’

177. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) 1. 2. 3. ’’On every checkout, give a discount based on the rate at login time’’

178. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) 1. 2. 3. 4. ’’On every checkout, give a discount based on the rate at login time’’

179. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) 1. 2. 3. 4. (4 gf-call set-rate <shop> 0.00) ’’On every checkout, give a discount based on the rate at login time’’

180. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) 1. 2. 3. 4. 5. (4 gf-call set-rate <shop> 0.00) ’’On every checkout, give a discount based on the rate at login time’’

181. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) 1. 2. 3. 4. 5. (4 gf-call set-rate <shop> 0.00) ’’On every checkout, give a discount based on the rate at login time’’

188. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) 1. 2. 3. 4. 5. (4 gf-call set-rate <shop> 0.00) (5 gf-call checkout <kris>) ’’On every checkout, give a discount based on the rate at login time’’

193. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) 1. 2. 3. 4. 5. (4 gf-call set-rate <shop> 0.00) (5 gf-call checkout <kris>) (2 gf-call login <kris> <shop>) ’’On every checkout, give a discount based on the rate at login time’’

196. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) 1. 2. 3. 4. 5. (4 gf-call set-rate <shop> 0.00) (5 gf-call checkout <kris>) (2 gf-call login <kris> <shop>) (escape 0.00 (current-rate <shop>)) ) ’’On every checkout, give a discount based on the rate at login time’’

197. ) Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) 1. 2. 3. 4. 5. (4 gf-call set-rate <shop> 0.00) (5 gf-call checkout <kris>) (2 gf-call login <kris> <shop>) (escape 0.00 (current-rate <shop>)) ) ’’On every checkout, give a discount based on the rate at login time’’

198. ) ) Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) 1. 2. 3. 4. 5. (4 gf-call set-rate <shop> 0.00) (5 gf-call checkout <kris>) (2 gf-call login <kris> <shop>) (escape 0.00 (current-rate <shop>)) ) ’’On every checkout, give a discount based on the rate at login time’’

199. ) ) Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) 1. 2. 3. 4. 5. (discount <kris> 0.00) ) (4 gf-call set-rate <shop> 0.00) (5 gf-call checkout <kris>) (2 gf-call login <kris> <shop>) (escape 0.00 (current-rate <shop>)) ) ’’On every checkout, give a discount based on the rate at login time’’

200. ) ) Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) 1. 2. 3. 4. 5. (discount <kris> 0.00) ) (4 gf-call set-rate <shop> 0.00) (5 gf-call checkout <kris>) (2 gf-call login <kris> <shop>) (escape 0.00 (current-rate <shop>)) ) ’’On every checkout, give a discount based on the rate at login time’’

201. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) ’’On every checkout, give a discount based on the rate at login time’’

202. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’

215. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1.

216. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. (1 gf-call set-rate <shop> 0.05)

223. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. (1 gf-call set-rate <shop> 0.05)

224. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>)

229. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (2 gf-call login <kris> <shop>)

230. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) )

231. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) )

232. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. 3. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) )

233. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. 3. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) )

234. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. 3. 4. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) )

235. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. 3. 4. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (4 gf-call set-rate <shop> 0.00) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) )

236. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. 3. 4. 5. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (4 gf-call set-rate <shop> 0.00) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) )

237. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. 3. 4. 5. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) (4 gf-call set-rate <shop> 0.00) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) )

238. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. 3. 4. 5. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) (4 gf-call set-rate <shop> 0.00) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) ) (5 gf-call checkout <kris>)

239. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. 3. 4. 5. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) (4 gf-call set-rate <shop> 0.00) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) ) (5 gf-call checkout <kris>)

240. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward Chaining ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. 3. 4. 5. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) (4 gf-call set-rate <shop> 0.00) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) ) (5 gf-call checkout <kris>) (discount <kris> 0.05) )

241. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward ChainingStateful ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. 3. 4. 5. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) (4 gf-call set-rate <shop> 0.00) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) ) (5 gf-call checkout <kris>) (discount <kris> 0.05) )

242. Backward Chaining Backward Chaining vs Rete Forward Chaining (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) and most-recent ?(discount ?user ?rate) ! query engine (set-rate *shop* 0.05) (login *kris* *shop*) (buy *kris* *cd*) (set-rate *shop* 0.00) (checkout *kris*) Rete Forward ChainingStateful ’’On every checkout, give a discount based on the rate at login time’’ 1. 2. 3. 4. 5. (1 gf-call set-rate <shop> 0.05) (2 gf-call login <kris> <shop>) (3 gf-call buy <kris> <cd>) (5 gf-call checkout <kris>) (4 gf-call set-rate <shop> 0.00) (2 gf-call login <kris> <shop>) (escape 0.05 (current-rate <shop>)) ) (5 gf-call checkout <kris>) (discount <kris> 0.05) ) Temporal Extensions Escape Extension

243. Reducing Memory Overhead (at ((gf-call checkout (?user)) (most-recent (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)))) (discount ?user ?rate)) (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) most-recent ?(discount ?user ?rate) escape T1 ?user T2 ?user ?shop T2 ?rate ?user ?shop T1 ?rate ?user ?shop (login *kris* *shop*) (buy *kris* *cd*) (checkout *kris*) (login *kris* *shop*) (buy *kris* *dvd*) (checkout *kris*) Code

244. Reducing Memory Overhead (at ((gf-call checkout (?user)) (most-recent (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)))) (discount ?user ?rate)) (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) most-recent ?(discount ?user ?rate) escape T1 ?user T2 ?user ?shop T2 ?rate ?user ?shop T1 ?rate ?user ?shop (login *kris* *shop*) (buy *kris* *cd*) (checkout *kris*) (login *kris* *shop*) (buy *kris* *dvd*) (checkout *kris*) 1 <kris> <shop> 3 <kris> 4 <kris> <shop>0.05 3 <kris> <shop>0.05 6 <kris> <shop>0.05 4 <kris> <shop> 1 <kris> <shop>0.05 6 <kris> Code

245. Reducing Memory Overhead (at ((gf-call checkout (?user)) (most-recent (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)))) (discount ?user ?rate)) (gf-call checkout (?user)) (gf-call login ?user ?shop) (escape ?rate (current-rate ?shop)) most-recent ?(discount ?user ?rate) escape T1 ?user T2 ?user ?shop T2 ?rate ?user ?shop T1 ?rate ?user ?shop (login *kris* *shop*) (buy *kris* *cd*) (checkout *kris*) (login *kris* *shop*) (buy *kris* *dvd*) (checkout *kris*) 1 <kris> <shop> 3 <kris> 4 <kris> <shop>0.05 3 <kris> <shop>0.05 6 <kris> <shop>0.05 4 <kris> <shop> 1 <kris> <shop>0.05 6 <kris> Code LT [1,1] [4,4] LT [1,4] [4,..] LT [3,3] [6,6] LT [3,3] [6,6]

246. DEMO

247. 0 2,000 4,000 6,000 8,000 S3 copy S3 non copy S2 copy S2 non copy S1 copy S1 non copy nr of memory table entries still allocated total nr of memory table entries ever made nr of generated join point facts Reducing Memory Overhead (2) Escaping with future variables in HALO Charlotte Herzeel, Kris Gybels, Pascal Costanza In "Proc. of the Runtime Veriﬁcation Workshop", 2007 Modularizing crosscuts in an e-commerce application in Lisp using HALO Charlotte Herzeel, Kris Gybels, Pascal Costanza, Theo D’Hondt In "Proc. of the International Lisp Conference", 2007

248. 0 2,000 4,000 6,000 8,000 S3 copy S3 non copy S2 copy S2 non copy S1 copy S1 non copy nr of memory table entries still allocated total nr of memory table entries ever made nr of generated join point facts Reducing Memory Overhead (2) It helps! Escaping with future variables in HALO Charlotte Herzeel, Kris Gybels, Pascal Costanza In "Proc. of the Runtime Veriﬁcation Workshop", 2007 Modularizing crosscuts in an e-commerce application in Lisp using HALO Charlotte Herzeel, Kris Gybels, Pascal Costanza, Theo D’Hondt In "Proc. of the International Lisp Conference", 2007

249. Summary & Future Work • Summary: • history-based AOP for CLOS ; stateful pointcuts • temporal logic-based: abstraction & logic variables • Rete forward chaining-based implementation • memory reduction • Future Work: • language design: • exploit logic-programming (i.e. unification & recursion) • exploit temporal logic-programming (mixing temporal logic/advice code) • before/after ... what about around? (roll-back mechanism) • reducing memory overhead: • shadow weaving

250. Summary & Future Work • Summary: • history-based AOP for CLOS ; stateful pointcuts • temporal logic-based: abstraction & logic variables • Rete forward chaining-based implementation • memory reduction • Future Work: • language design: • exploit logic-programming (i.e. unification & recursion) • exploit temporal logic-programming (mixing temporal logic/advice code) • before/after ... what about around? (roll-back mechanism) • reducing memory overhead: • shadow weaving Thanks for listening! Questions?

251. Summary & Future Work • Summary: • history-based AOP for CLOS ; stateful pointcuts • temporal logic-based: abstraction & logic variables • Rete forward chaining-based implementation • memory reduction • Future Work: • language design: • exploit logic-programming (i.e. unification & recursion) • exploit temporal logic-programming (mixing temporal logic/advice code) • before/after ... what about around? (roll-back mechanism) • reducing memory overhead: • shadow weaving Thanks for listening! Questions? http://prog.vub.ac.be/HALO

252. References • Supporting Software Development Through Declaratively Codified Programming Patterns, Kim Mens, Isabel Michiels, Roel Wuyts In "Journal on Expert Systems with Applications, Elsevier Publications, pages 405-413, number 4, Volume 23, November", 2002 • Arranging language features for more robust pattern-based crosscuts Kris Gybels, Johan Brichau, In "Proceedings of the Second International Conference on Aspect- Oriented Software Development", 2003 • Seamless Integration of Rule-Based Knowledge and Object-Oriented Functionality with Linguistic Symbiosis, Maja D'Hondt, Kris Gybels, Viviane Jonckers, In "Proceedings of the 19th Annual ACM Symposium on Applied Computing (SAC 2004), Special Track on Object-Oriented Programming, Languages and Systems. Nicosia, Cyprus. ACM. March 2004.", 2004 • Context-aware Aspects, Eric Tanter, Kris Gybels, Marcus Denker, Alexandre Bergel, Proceedings of the 5th International Symposium on Software Composition (SC 2006), LNCS 4089, pp.227-249, Springer-Verlag, March 2006, Vienna, Austria • Expressive Pointcuts for Increased Modularity, Klaus Ostermann and Mira Mezini and Christoph Bockisch, Proceedings of the European Conference on Object-Oriented Programming (ECOOP) • Modularizing Crosscuts in an E-commerce Application in Lisp using HALO , Charlotte Herzeel, Kris Gybels, Pascal Costanza, Theo D'Hondt , International Lisp Conference 2007 • Escaping with future variables in HALO , Charlotte Herzeel, Kris Gybels, Pascal Costanza, Proceedings of the Runtime Verification Workshop 2007

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