Our domain-specific language for defining workflows in WebDSL.

1. WebWorkFlow
An Object-Oriented Workflow
Modeling Language
Zef Hemel, Ruben Verhaaf, Eelco Visser
Delft University of Technology, The Netherlands

2. WebWorkFlow
coordination

3. BPEL

4. BPEL
Petri nets

5. BPEL YAWL
Petri nets

6. BPEL YAWL
Petri nets
✘ do not describe full applications
✘ separate language, not nicely integrated
✘ ignore user interface
✘ all or nothing

8. WebWorkFlow
3 design principles

9. Linguistic integration

10. abstraction layers

11. Process Expressions
Procedural Workflow
WebDSL

12. concise Process Expressions
(less flexible)
Procedural Workflow
more verbose WebDSL
(more flexible)

13. Full application generation

14. JBoss Seam
Google Java
AppEngine Servlet

15. Scenario

16. hank

17. his employees

18. preparation

19. meeting

20. manager
write report

21. write report
employee
approve comment

22. write report
approve comment
manager
finalize

23. sue

31. WebWorkFlow

32. concise Process Expressions
(less flexible)
Workflow Procedures
more verbose WebDSL
(more flexible)

33. ...
WebDSL
Data Model User Interface Access Control
Core WebDSL
Core Data Model Core User Interface
Web Application

34. Data models User Interface Logic Access control

35. entity User {
username :: String
password :: Secret
name :: String
manager -> User
employees -> Set<User>
}

36. define page editUser(u : User) {
form {
table {
row { "Name: " input(u.name) }
row { "Manager: " input(u.manager) }
row { "Employees: " input(u.employees) }
}
action("Save", save())
action save() {
u.save();
return home();
}
}
}

37. define page editUser(u : User) {
derive editPage from u
for (name, manager, employees)
}

38. access control rules
page editUser(u : User) {
principal == u.manager
}

39. Data models User Interface Logic Access control

40. Data models User Interface Logic Access control Workflow

41. Workflows revolve around objects
entity Meeting {
employee -> User
employeeView :: Text
managerView :: Text
report :: Text
approved :: Bool
comment :: Text
}

42. Workflows revolve around objects
entity Meeting {
employeePrepare employee -> User
managerPrepare employeeView :: Text
writeReport managerView :: Text
approveReport
report :: Text
commentReport
finalizeReport approved :: Bool
comment :: Text
}
and operations (procedures)
performed on them

43. module workflow
procedure writeReport(m : Meeting) {
who { principal == m.employee.manager }
view {
derive procedurePage from m for (report)
}
}

44. part of a WebDSL module
module workflow
procedure writeReport(m : Meeting) {
who { principal == m.employee.manager }
view {
derive procedurePage from m for (report)
}
}

45. part of a WebDSL module
module workflow
procedure writeReport(m : Meeting) {
who { principal == m.employee.manager }
view {
derive procedurePage from m for (report)
}
}
access control expression language

46. part of a WebDSL module
module workflow
procedure writeReport(m : Meeting) {
who { principal == m.employee.manager }
view {
derive procedurePage from m for (report)
}
}
access control expression language
view page language

47. concise Process Expressions
(less flexible)
Procedural Workflow
more verbose WebDSL
(more flexible)

48. procedure procedureName(o : Entity) {
who { who can perform }
when { additional condition }
view { view page }
enabled { action code }
disabled { action code }
do { action code }
done { action code }
}

49. actor
who { principal == m.employee }

50. condition
when { now() > m.startDate }

51. user interface
view { derive procedurePage from m
for (employeePreparation) }

52. action
do {
email(organizeMeetingMail(m));
}

53. events
done {
m.writeReport.enable();
}
enabled
disabled
done

54. concise Process Expressions
(less flexible)
Workflow Procedures
more verbose WebDSL
(more flexible)

55. procedure meetingWorkflow(m : Meeting) {
process {
(employeePrepare(m) and managerPrepare(m));
repeat {
writeReport(m);
(approveReport(m) xor commentReport(m))
} until finalizeReport(m)
}
}

56. sequence ;

57. sequence ;
parallel and

58. sequence ;
parallel and
deferred choice +

59. sequence ;
parallel and parallel xor
deferred choice +

60. sequence ;
parallel and parallel xor
deferred choice + repeat ... until loops

61. sequence ;
parallel and parallel xor
deferred choice + repeat ... until loops
conditional if ... else

62. Transforming
Procedures

63. WebWorkFlow
User Access Procedure Process
Data Model
Interface Control Events Expressions
Procedural WebWorkFlow
Access Procedure
Data Model User Interface
Control Events
WebDSL
Data Model User Interface Access Control
Core WebDSL
Core Data Model Core User Interface
Web Application

64. concise WebWorkFlow
(high-level) User Access Procedure Process
Data Model
Interface Control Events Expressions
Procedural WebWorkFlow
Access Procedure
Data Model User Interface
Control Events
compilation
by WebDSL
normalization Data Model User Interface Access Control
Core WebDSL
Core Data Model Core User Interface
verbose Web Application
(low-level)

65. concise WebWorkFlow
(high-level) User Access Procedure Process
Data Model
Interface Control Events Expressions
Procedural WebWorkFlow
Access Procedure
Data Model User Interface
Control Events
compilation
by WebDSL
normalization Data Model User Interface Access Control
Core WebDSL
Core Data Model Core User Interface
verbose Web Application
(low-level)

66. concise WebWorkFlow
(high-level) User Access Procedure Process
Data Model
Interface Control Events Expressions
Procedural WebWorkFlow
Access Procedure
Data Model User Interface
Control Events
compilation
by WebDSL
normalization Data Model User Interface Access Control
Core WebDSL
Core Data Model Core User Interface
verbose Web Application
(low-level)

67. state
user interface
access control

68. Example
procedure writeReport(m : Meeting) {
who { principal == m.employee.manager }
view {
derive procedurePage from m for (report)
}
done {
m.approveReport.enable();
m.commentReport.enable();
}
}

69. procedure writeReport(m : Meeting) {
who { principal == m.employee.manager }
view {
derive procedurePage from m for (report)
}
done {
m.approveReport.enable();
m.commentReport.enable();
}
}
Procedure (=workflow) state is kept
extend entity Meeting {
writeReport -> WriteReportProcedureStatus
}
in the object it operates on

70. entity WriteReportProcedureStatus : ProcedureStatus {
...
}
entity ProcedureStatus {
isEnabled :: Bool
function enable() {
isEnabled := true;
}
function disable() {
isEnabled := false;
}
}

71. procedure writeReport(m : Meeting) {
who { principal == m.employee.manager }
view {
derive procedurePage from m for (report)
}
done {
m.approveReport.enable();
m.commentReport.enable();
}
}
define page writeReport(m : Meeting) {
derive procedurePage from m for (employeeView)
}
user interface

72. procedure writeReport(m : Meeting) {
who { principal == m.employee.manager }
view {
derive procedurePage from m for (report)
}
done {
m.approveReport.enable();
m.commentReport.enable();
}
}
access control rules
rule page writeReport(m : Meeting) {
principal == m.employee.manager &&
m.writeReport.isEnabled
}
access control

73. procedure writeReport(m : Meeting) {
who { principal == m.employee.manager }
view {
derive procedurePage from m for (report)
}
done {
m.approveReport.enable();
m.commentReport.enable();
}
}
extend entity WriteReportProcedureStatus {
m -> Meeting
function done() {
m.approveReport.enable();
m.commentReport.enable();
}
}
control logic

74. WebWorkFlow
User Access Procedure Process
Data Model
Interface Control Events Expressions
Procedural WebWorkFlow
Access Procedure
Data Model User Interface
Control Events
WebDSL
Data Model User Interface Access Control
Core WebDSL
Core Data Model Core User Interface
Web Application

75. WebWorkFlow
User Access Procedure Process
Data Model
Interface Control Events Expressions
Procedural WebWorkFlow
Access Procedure
Data Model User Interface
Control Events
WebDSL
Data Model User Interface Access Control
Core WebDSL
Core Data Model Core User Interface
Web Application

76. encode control flow

77. encode control flow
in procedure events
enabled
disabled
done

78. procedure p(o : O) {
process {
a(o);
b(o)
}
}

79. procedure p(o : O) {
process {
a(o);
b(o)
}
}
extend procedure a(o : O) {
done {
o.b.enable();
}
}

80. procedure p(o : O) {
process {
a(o);
b(o)
}
}
extend procedure a(o : O) {
done {
o.b.enable();
}
}
...right?

81. procedure p(o : O) {
process {
a(o);
b(o);
a(o)
}
}

82. procedure p(o : O) {
process {
a(o);
b(o);
a(o)
}
}
extend procedure a(o : O) {
done {
??
}
}

83. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
+ transition function

84. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
p(o) state next
0 a.enable(this, 1)
1 b.enable(this, 2)
2 a.enable(this, 3)
a(o) b(o) 3 done

85. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
p(o) state next
0 a.enable(this, 1)
1 b.enable(this, 2)
2 a.enable(this, 3)
a(o) b(o) 3 done

86. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
p(o) state next
0 a.enable(this, 1)
[1]
1 b.enable(this, 2)
2 a.enable(this, 3)
a(o) b(o) 3 done

87. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
p(o) state next
0 a.enable(this, 1)
1 b.enable(this, 2)
2 a.enable(this, 3)
a(o) b(o) 3 done
[1]

88. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
p(o) state next
0 a.enable(this, 1)
[1]
1 b.enable(this, 2)
2 a.enable(this, 3)
a(o) b(o) 3 done

89. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
p(o) state next
0 a.enable(this, 1)
[2]
1 b.enable(this, 2)
2 a.enable(this, 3)
a(o) b(o) 3 done

90. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
p(o) state next
0 a.enable(this, 1)
1 b.enable(this, 2)
2 a.enable(this, 3)
a(o) b(o) 3 done
[2]

91. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
p(o) state next
0 a.enable(this, 1)
1
[2]
b.enable(this, 2)
2 a.enable(this, 3)
a(o) b(o) 3 done

92. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
p(o) state next
0 a.enable(this, 1)
[3]
1 b.enable(this, 2)
2 a.enable(this, 3)
a(o) b(o) 3 done

93. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
p(o) state next
0 a.enable(this, 1)
1 b.enable(this, 2)
2 a.enable(this, 3)
a(o)
[3]
b(o) 3 done

94. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
p(o) state next
0 a.enable(this, 1)
[3]
1 b.enable(this, 2)
2 a.enable(this, 3)
a(o) b(o) 3 done

95. procedure p(o : O) {
process {
a(o)[1];
b(o)[2];
a(o)[3]
}
}
p(o) state next
0 a.enable(this, 1)
1 b.enable(this, 2)
2 a.enable(this, 3)
a(o) b(o) 3 done

96. next function for sequencing
entity SeqProcedureStatus : ... {
o -> O
function next(state : Int) {
if(state == 0) {
procedure p(o : O) { o.a.enable(this, 1);
process { }
a(o)[1]; if(state == 1) {
b(o)[2]; o.b.enable(this, 2);
a(o)[3] }
} if(state == 2) {
} o.a.enable(this, 3);
}
if(state == 3) {
processed();
}
}
}

97. next function for parallel and
entity ParProcedureStatus : ... {
o -> O
counter :: Int
function next(state : Int) {
if(state == 0) {
o.a.enable(this, 1);
o.b.enable(this, 2);
procedure par(o : O) { }
process { if(state == 1) {
a(o)[1] and b(o)[2] counter := counter + 1;
if(counter == 2) {
} processed();
} }
}
if(state == 2) {
counter := counter + 1;
if(counter == 2) {
processed();
}
}
}
}

98. Encoding
Patterns

102. concise Process Expressions
(less flexible)
Procedural Workflow
more verbose WebDSL
(more flexible)

103. concise Process Expressions
(less flexible)
Procedural Workflow
more verbose WebDSL
(more flexible)

104. WebWorkFlow
linguistic integration

105. WebWorkFlow
linguistic integration
abstraction layers

106. WebWorkFlow
linguistic integration
abstraction layers
full application generation

107. WebWorkFlow
linguistic integration
abstraction layers
full application generation
compilation by normalization

108. www.webdsl.org
www.strategoxt.org

109. state tracking

110. state tracking task pages

111. state tracking task pages navigation

112. state tracking task pages navigation
task lists

113. state tracking task pages navigation
task lists workflow status

114. state tracking task pages navigation
task lists workflow status access control
rules

115. state tracking task pages navigation
task lists workflow status access control
rules
the rest