developing domain specific languages
Heiko Behrens
Eclipse DemoCamp 2009
London 29.07.2009
E-Mail Heiko.Behrens@itemis.de
Blog www.1160pm.net

Xtext?
Xtext is a framework for development of
external textual DSLs.
A domain specific language (DSL)
in the context of modeling
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.

Rd2-c2

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

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.n
P
iece S q uare io
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

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

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

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

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';

ik
at
Modell
m
m
ra
G
Superclass
Subclass Class
LL(*) Parser ecore meta model editor
Xtext framework (customizable with Google Guice)

Demo
• Model File
• 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 10

Entities (1/2)
@SuppressWarnings("serial")
@Entity
@Table(name = "CUSTOMER_INFO")
public class CustomerInfo implements Serializable {
! @Id
! @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "idSeq")
! @SequenceGenerator(name = "idSeq", sequenceName = "CUST_SEQ", allocationSize = 1)
! @Column(name = "CUST_ID", nullable = false)
! private String customerId;
! public void setCustomerId(String customerId) {
! ! this.customerId = customerId;
! }
! public String getCustomerId() {
! ! return customerId;
! }
! @Column(name = "EMAIL", nullable = false, length = 128)
! private String emailAddress;
! public String getEmailAddress() {
! ! return emailAddress;
! }
! public void setEmailAddress(String emailAddress) {
! ! String oldValue = emailAddress;
! ! this.emailAddress = emailAddress;
! ! firePropertyChangedEvent("emailAddress", oldValue, this.emailAddress);
! }

Entities (2/2)
entity CustomerInfo
! (id=CUST_ID, sequenceName=CUST_SEQ) {
!
! String emailAddress (notNull, length = 128)
!
}

DSLs in real world scenarios
modeling data
describe architectures
configuration
business rules
documentation
data mappings
navigation on object graphs
constraints
knitting patterns
...

Demo
! Graphical EMF model
! Enhanced with textual DSL (with Xtext)
! Validation
! Code Generation
! Changes textual DSL

Language development has never been so easy.

amoun%
&nit' (am)
ingredient'
*rocedur)

Demo
recipe:
"pizza without yeast"
ingredients:
125g curd
1 egg
20ml oil
40ml milk
5g salt
250g flour
1x ! soda
procedure:
"Combine all ingredients. Make it a ball.
Knead 10 times. Put dough on a greased cookie sheet
and roll."
© itemis AG 2009 – All rights reserved 17

Where to go next?
www.xtext.org
twitter: Xtext
xtext.itemis.com
twitter: itemis
me www.1160pm.net
Heiko Behrens twitter: HBehrens