The document discusses the development of domain-specific languages (DSLs) using Xtext, a tool for creating textual programming languages within the Eclipse environment. It provides examples of DSL application, showcasing practical coding of simple chess games, complex event processing, and entity modeling. Additionally, it highlights the abstraction and incremental generation benefits of DSLs, while promoting community resources and professional support links.

1. Building DSLs with Xtext
Eclipse Modeling Day
New York, 16 November 2009
Toronto, 18 November 2009
Heiko Behrens (itemis)
© itemis AG 2009 – All rights reserved

2. FOUNDATION
MEMBER TM

4. Model-Driven Software Development
with DSLs

6. Suppose...

7. You’d want to core an apple...

8. ... for your kids.

9. ?
Right tool for the job?

10. Your trusty swiss army knife!

11. Suppose...

12. You’d want to core a few more apples...

13. ... for an apple cake.

14. Still the best tool for the job?

15. Better use this one.

16. and this one:

17. ... a DSL is ...

18. A specific tool
for a specific job

19. A specific tool
for a specific job

20. Domain-Specific Language (DSL)
A DSL is a formal, processable language
targeting at a specific viewpoint or
aspect of a software system.
Its semantics, flexibility and notation is
designed in order to support working
with that viewpoint as good as possible.

21. Rd2-c2

22. “ Queen to c7.
Check.”
“ Rd2-c2 ,
”
rook at d2 moves to c2.

23. Moves in Chess:
!ook at a1 moves to a5.
P
iece S q uare A
ction
De stin ation
"ishop at c8 captures knight at h3.
P
iece S q uare ion
Action
D
es tinat
# b1 x c3
Piece S qua re ction stination
AD e
$2 - g4
ation
S A D
quar
e ction e stin

24. Rook a1 move a5
Bishop c8 capture h3 Knight
Knight b1 capture c3 Queen
Pawn g2 move g4
Game Move
Source «enum»
WhitePlayer
* Destination Piece
BlackPlayer
Piece

25. "ishop at c8 captures knight at h3
" c8 x h3

26. Model (textfile)
White: "Mayfield"
Black: "Trinks"
pawn at e2 moves to e4
pawn at f7 moves to g5
K b1 - c3
f7 - f5
queen at d1 moves to h5
// 1-0

28. Xtext is a complete environment
for development of textual
- programming languages and
- domain-specific languages.
It is implemented in Java and is
based on Eclipse, EMF, and Antlr.

29. ar
Model
m
m
ra
G
Generator
Runtime
Superclass
Subclass Class
LL(*) Parser ecore meta model editor

30. Grammar (similar to EBNF)
Game:
! "White:" whitePlayer=STRING
! "Black:" blackPlayer=STRING
! (moves+=Move)+;
!
Move:
! AlgebraicMove | SpokenMove;
AlgebraicMove:
! (piece=Piece)? source=Square (captures?='x'|'-') dest=Square;
!
SpokenMove:
! piece=Piece 'at' source=Square
! (captures?='captures' capturedPiece=Piece 'at' | 'moves to')
! dest=Square;
!
terminal Square:
! ('a'..'h')('1'..'8');
!
enum Piece:
! pawn = 'P' | pawn = 'pawn' |
! knight = 'N' | knight = 'knight' |
! bishop = 'B' | bishop = 'bishop' |
! rook = 'R' | rook = 'rook' |
! queen = 'Q' | queen = 'queen' |
! king = 'K' | king = 'king';

31. Demo
• Model File within Editor + Custom View
• Xtext Grammar for writing simple chess games
• Derived meta model
• Java program that works with textual models
• Xpand-based generator
© itemis AG 2009 – All rights reserved 31

32. Real World DSLs

33. Regular Expressions

34. [-+]?[0-9]*.?[0-9]+

35. Complex Event Processing

36. from FlightBookings F, CarBookings C, HotelBookings H
matching [24 hours: F, C, H ]
on F.name = C.name = H.name
select F.name, true bookingWithCar,
into TripleBookings
from FlightBookings F, CarBookings C, HotelBookings H
matching [24 hours: F, !C, H ]
on F.name = C.name = H.name
select F.name, false bookingWithCar
into TripleBookings
from TripleBookings
where prev(bookingWithCar) and not bookingWithCar
select name
into LostCustomers

37. internal DSL
(with Java)

38. Mailer.mail()
.to(“you@gmail.com”)
.from(“me@gmail.com”)
.subject(“Writing DSLs in Java”)
.body(“...”)
.send();

39. ANT

40. <project name="MyProject" default="dist" basedir=".">
<property name="src" location="src"/>
<property name="build" location="build"/>
<property name="dist" location="dist"/>
<target name="init">
<mkdir dir="${build}"/>
</target>
<target name="compile" depends="init">
<javac srcdir="${src}" destdir="${build}"/>
</target>
<target name="dist" depends="compile">
<mkdir dir="${dist}/lib"/>
<jar jarfile="${dist}/lib/MyProject.jar"
basedir="${build}"/>
</target>
<target name="clean">
<delete dir="${build}"/>
<delete dir="${dist}"/>
</target>
</project>

41. ANT
?

42. <project name="MyProject" default="dist" basedir=".">
<property name="src" location="src"/>
<property name="build" location="build"/>
<property name="dist" location="dist"/>
<target name="init">
<mkdir dir="${build}"/>
</target>
<target name="compile" depends="init">
<javac srcdir="${src}" destdir="${build}"/>
</target>
<target name="dist" depends="compile">
<mkdir dir="${dist}/lib"/>
<jar jarfile="${dist}/lib/MyProject.jar"
basedir="${build}"/>
</target>
<target name="clean">
<delete dir="${build}"/>
<delete dir="${dist}"/>
</target>
</project>

43. Entities by Example
vs.

44. package templates;
import java.util.*;
import java.io.Serializable;
import javax.persistence.*;
@SuppressWarnings("serial")
@Entity
public class Customer implements Serializable {
! private Long id;
! private String name;
! private Address address;
! private Set<Order> orders = new HashSet<Order>();
! // No-arg constructor
! public Customer() {
! }
! @Id
! public Long getId() {
! ! return id;
! }
! public void setId(Long id) {
! ! this.id = id;
! }
! public String getName() {
! ! return name;
! }
! public void setName(String name) {
! ! this.name = name;
! }
! public Address getAddress() {
! ! return address;
! }
! public void setAddress(Address address) {
! ! this.address = address;
! }
! @OneToMany
! public Collection<Order> getOrders() {
! ! return orders;
! }
! public void setOrders(Set<Order> orders) {
! ! this.orders = orders;
! }
}

45. package templates;
import java.io.Serializable;
import java.util.*;
import javax.persistence.*;
@SuppressWarnings("serial")
@Entity
public class Customer implements Serializable {
! private Long id;
! private String name;
! private Address address;
! private Set<Order> orders = new HashSet<Order>();
! // No-arg constructor
! public Customer() {
! }
! @Id
! public Long getId() {
! ! return id;
! }
! public void setId(Long id) {
! ! this.id = id;
! }
! public String getName() {
! ! return name;
! }
! public void setName(String name) {
! ! this.name = name;
! }
! public Address getAddress() {
! ! return address;
! }
! public void setAddress(Address address) {
! ! this.address = address;
! }
! @OneToMany
! public Collection<Order> getOrders() {
! ! return orders;
! }
! public void setOrders(Set<Order> orders) {
! ! this.orders = orders;
! }
}

46. entity Customer {
! property name : String
! property address : Address
! property orders : Order[]
}
POJOs DAOs

47. The Finder Method

48. <entity name="Customer">
<attribute type="String" name="name"/>
<findMethod name="findFixed">
<expression>
<equals>
<attributeRef attr="name"/>
<constant val="John Doe"/>
</equals>
</expression>
<findMethod>
</entity>
entity Customer {
! property name : String
! finder findFixed : name = "John Doe"
}

49. Demo
! Implement simple Entity DSL
! Use prepared Generator

50. grammar org.xtext.webinar.Entity
! with org.eclipse.xtext.common.Terminals
entity
generate entity
"http://www.xtext.org/webinar/Entity" Model
Model:
types
! (elements+=Type)*;
*
Type: Type
name: EString
! SimpleType | Entity;
SimpleType:
! 'type' name=ID;
SimpleType Entity
Entity: extends
! 'entity' name=ID
('extends' extends=[Entity])? '{'
properties
! ! properties+=Property* *
! '}'; Property
name: EString
type many: EBoolean
Property:
! 'property' name=ID ':'
type=[Type] (many?='[]')?;

51. grammar org.xtext.webinar.Entity
! with org.eclipse.xtext.common.Terminals
entity
generate entity
"http://www.xtext.org/webinar/Entity" Model
Model:
types
! (elements+=Type)*;
*
Type: Type
name: EString
! SimpleType | Entity;
SimpleType:
! 'type' name=ID;
SimpleType Entity
Entity: extends
! 'entity' name=ID
('extends' extends=[Entity])? '{'
properties
! ! properties+=Property* *
! '}'; Property
name: EString
type many: EBoolean
Property:
! 'property' name=ID ':'
type=[Type] (many?='[]')?;

52. grammar org.xtext.webinar.Entity
! with org.eclipse.xtext.common.Terminals
entity
generate entity
"http://www.xtext.org/webinar/Entity" Model
Model:
types
! (elements+=Type)*;
*
Type: Type
name: EString
! SimpleType | Entity;
SimpleType:
! 'type' name=ID;
SimpleType Entity
Entity: extends
! 'entity' name=ID
('extends' extends=[Entity])? '{'
properties
! ! properties+=Property* *
! '}'; Property
name: EString
type many: EBoolean
Property:
! 'property' name=ID ':'
type=[Type] (many?='[]')?;

53. grammar org.xtext.webinar.Entity
! with org.eclipse.xtext.common.Terminals
entity
generate entity
"http://www.xtext.org/webinar/Entity" Model
Model:
types
! (elements+=Type)*;
*
Type: Type
name: EString
! SimpleType | Entity;
SimpleType:
! 'type' name=ID;
SimpleType Entity
Entity: extends
! 'entity' name=ID
('extends' extends=[Entity])? '{'
properties
! ! properties+=Property* *
! '}'; Property
name: EString
type many: EBoolean
Property:
! 'property' name=ID ':'
type=[Type] (many?='[]')?;

54. grammar org.xtext.webinar.Entity
! with org.eclipse.xtext.common.Terminals
entity
generate entity
"http://www.xtext.org/webinar/Entity" Model
Model:
types
! (elements+=Type)*;
*
Type: Type
name: EString
! SimpleType | Entity;
SimpleType:
! 'type' name=ID;
SimpleType Entity
Entity: extends
! 'entity' name=ID
('extends' extends=[Entity])? '{'
properties
! ! properties+=Property* *
! '}'; Property
name: EString
type many: EBoolean
Property:
! 'property' name=ID ':'
type=[Type] (many?='[]')?;

55. grammar org.xtext.webinar.Entity
! with org.eclipse.xtext.common.Terminals
entity
generate entity
"http://www.xtext.org/webinar/Entity" Model
Model:
types
! (elements+=Type)*;
*
Type: Type
name: EString
! SimpleType | Entity;
SimpleType:
! 'type' name=ID;
SimpleType Entity
Entity: extends
! 'entity' name=ID
('extends' extends=[Entity])? '{'
properties
! ! properties+=Property* *
! '}'; Property
name: EString
type many: EBoolean
Property:
! 'property' name=ID ':'
type=[Type] (many?='[]')?;

56. grammar org.xtext.webinar.Entity
! with org.eclipse.xtext.common.Terminals
entity
generate entity
"http://www.xtext.org/webinar/Entity" Model
Model:
types
! (elements+=Type)*;
*
Type: Type
name: EString
! SimpleType | Entity;
SimpleType:
! 'type' name=ID;
SimpleType Entity
Entity: extends
! 'entity' name=ID
('extends' extends=[Entity])? '{'
properties
! ! properties+=Property* *
! '}'; Property
name: EString
type many: EBoolean
Property:
! 'property' name=ID ':'
type=[Type] (many?='[]')?;

57. Pimp
my Write

59. Whitespace-Aware
Languages

60. Incremental
Generation

61. Conclusion

62. Abstraction

63. Use a DSL to develop your tools

64. Support
Newsgroup
Community Forum
Professional Support

65. twitter @HBehrens
blog http://HeikoBehrens.net
mail Heiko.Behrens@itemis.de
xing http://www.xing.com/profile/Heiko_Behrens
linkedin http://www.linkedin.com/in/HeikoBehrens
www.xtext.org
The Committer Team twitter @Xtext
Heiko Michael Sven Moritz Peter Dennis Jan Patrick Knut Sebastian
Behrens Clay Efftinge Eysholdt Friese Hübner Köhnlein Schönbach Wannheden Zarnekow