Domain-specific languages explained by expert Dr. Jan Köhnlein

Domain-specific languages
with

Dr. Jan Köhnlein

itemis AG

• Software Architect, Consultant,
Coach at itemis

Jan Köhnlein

Coach at itemis
• Several years of experience
in the modeling world

Jan Köhnlein

Coach at itemis
• Several years of experience
in the modeling world
• Committer to several open-
source projects

Jan Köhnlein

itemis short facts

 Spezialist für modellbasierte Entwicklungsverfahren
 Gründung im Jahr 2003
 Niederlassungen in Deutschland, Frankreich,
Schweiz und Kanada
 140 Mitarbeiter
 Strategisches Mitglied der Eclipse Foundation
 Intensive Verzahnung im Bereich der Forschung
 Mitglied von ARTEMISIA
 Embedded Software Development
 Enterprise Application Development

1

What is a
Domain Speciﬁc
Language (DSL)?

A domain-speciﬁc language (DSL)
is a formal, processable language
targeting at a speciﬁc viewpoint or aspect
of a system.

A domain-specific language (DSL)
is a formal, processable language
targeting at a specific viewpoint or aspect
of a system.

Its semantics, flexibility and notation is designed
in order to support working with that viewpoint
as good as possible.

Boring! Don‘t
you have any
examples?

“ Queen to c7.
Check.”

“ Rd2-c2 ,
rook at d2 moves to c2.”

@Entity
public class Customer implements Serializable {
private Long id;
private String name;
private Address address;
private Collection<Order> orders = new HashSet<Order>();
private Set<PhoneNumber> phones = new HashSet<PhoneNumber>();

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(Collection<Order> orders) {
this.orders = orders;
}
@ManyToMany
public Set<PhoneNumber> getPhones() {
return phones;
}
public void setPhones(Set<PhoneNumber> phones) {
this.phones = phones;
}
}

@Entity
public class Customer implements Serializable {
private Long id;
private String name;
private Address address;
private Collection<Order> orders = new HashSet<Order>();
private Set<PhoneNumber> phones = new HashSet<PhoneNumber>();

public Customer() {}
@Id
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
} entity Customer {
public void setName(String name) {
this.name = name;
String name
} Address address
public Address getAddress() {
return address; Order* orders
}
public void setAddress(Address address) {
PhoneNumber** phones
this.address = address; }
}
@OneToMany
public Collection<Order> getOrders() {
return orders;
}
public void setOrders(Collection<Order> orders) {
this.orders = orders;
}
@ManyToMany
public Set<PhoneNumber> getPhones() {
return phones;
}
public void setPhones(Set<PhoneNumber> phones) {
this.phones = phones;
}
}

Expr

2+3*7/8
Op +

Parser Number 2 Op /

Op * Number 8

Number 3 Number 7

public class ParserTests extends TestCase {

public void testExampleExpression2() throws IOException {
EObject ast = parse("2+3*7/8");
assertTrue(ast instanceof Expr);
EObject ast_0 = child(ast, 0);
assertTrue(ast_0 instanceof Op);
assertEquals("+", ((Op) ast_0).getOperator());

EObject ast_0_0 = child(ast_0, 0);
assertTrue(ast_0_0 instanceof Number);
assertEquals(2, ((Number) ast_0_0).getValue());
assertTrue(ast_0_1 instanceof Op);
assertEquals("/", ((Op) ast_0_1).getOperator());

EObject ast_0_1_0 = child(ast_0_1, 0);
assertTrue(ast_0_1_0 instanceof Op);
assertEquals("*", ((Op) ast_0_1_0).getOperator());
assertTrue(ast_0_1_1 instanceof Number);
assertEquals(8, ((Number) ast_0_1_1).getValue());

EObject ast_0_1_0_0 = child(ast_0_1_0, 0);
assertTrue(ast_0_1_0_0 instanceof Number);
assertEquals(3, ((Number) ast_0_1_0_0).getValue());
assertTrue(ast_0_1_0_1 instanceof Number);
assertEquals(7, ((Number) ast_0_1_0_1).getValue());
}

public class ParserTests extends ParserTestCase {

public void testExampleExpression() throws IOException {
EObject ast_0 = child(ast, 0);
assertOperator(ast_0, "+");

assertNumber(ast_0_0, 2);
assertOperator(ast_0_1, "/");

assertOperator(ast_0_1_0, "*");
assertNumber(ast_0_1_1,8);

assertNumber(ast_0_1_0_0, 3);
}
}

public class ParserTests extends ParserTestCase {

public void testExampleExpression() throws IOException {
EObject ast_0 = child(ast, 0); test testExampleExpression
assertOperator(ast_0, "+"); "2+3*7/8"

EObject ast_0_0 = child(ast_0, 0); Expr {
assertNumber(ast_0_0, 2); Op operator="+" {
EObject ast_0_1 = child(ast_0, 1); Number value="2"
assertOperator(ast_0_1, "/"); Op operator="/" {
Op operator="*" {
EObject ast_0_1_0 = child(ast_0_1, 0); Number value="3"
assertOperator(ast_0_1_0, "*"); Number value="7"
EObject ast_0_1_1 = child(ast_0_1, 1); }
assertNumber(ast_0_1_1,8); Number value="8"
}
EObject ast_0_1_0_0 = child(ast_0_1_0, 0); }
assertNumber(ast_0_1_0_0, 3); }
}
}

What can I
achieve with
DSLs?

Why isn‘t
everybody using
DSLs?

licensed by http://www.wordle.net/

Reference

ar
Model

m
m
ra
G

Reference

ar
Model

m
m
ra
G
Runtime
Superclass

Subclass Class

ecore meta model LL(*) Parser editor

Runtime
Superclass

Subclass Class


Runtime
Superclass

Subclass Class


Model
Model
Model

Runtime
Superclass

Subclass Class


AST
Model
Model
Model

Runtime
Superclass

Subclass Class


Interpreter AST
Model
Model
Code Model
Generator

Example Model
type String

entity Conference {
property Name: String
n[]
property Attendees: Perso
er[]
property Speakers: Speak
}

entity Person {
}
rson {
entity Speaker extends Pe
n[]
property Sessions: Sessio
}

entity Session {
property Title: String
}

Example Model
entity
type String
Model
entity Conference {
property Name: String types
n[]
property Attendees: Perso *
er[]
property Speakers: Speak Type
} name: EString

entity Person {
} SimpleType Entity
extends
rson {
entity Speaker extends Pe
n[]
property Sessions: Sessio
properties
*
} Property
name: EString
entity Session { type many: EBoolean
property Title: String
}

grammar org.xtext.webinar.Entity
with org.eclipse.xtext.common.Terminals

generate entity
"http://www.xtext.org/webinar/Entity"

Model:
(elements+=Type)*;

Type:
SimpleType | Entity;

SimpleType:
'type' name=ID;

Entity:
'entity' name=ID
('extends' extends=[Entity])? '{'
properties+=Property*
'}';

Property:
'property' name=ID ':'
type=[Type] (many?='[]')?;

Grammar grammar org.xtext.webinar.Entity
definition with org.eclipse.xtext.common.Terminals

generate entity

Model:
(elements+=Type)*;

Type:

SimpleType:
'type' name=ID;

Entity:
'entity' name=ID
'}';

Property:

grammar org.xtext.webinar.Entity Grammar
with org.eclipse.xtext.common.Terminals reuse

generate entity

Model:
(elements+=Type)*;

Type:

SimpleType:
'type' name=ID;

Entity:
'entity' name=ID
'}';

Property:


Derived generate entity
metamodel

Model:
(elements+=Type)*;

Type:

SimpleType:
'type' name=ID;

Entity:
'entity' name=ID
'}';

Property:


generate entity

Model:
(elements+=Type)*;

Type:

Parser SimpleType:
rules 'type' name=ID;

Entity:
'entity' name=ID
'}';

Property:


generate entity

Model:
(elements+=Type)*;

Type:

SimpleType:
'type' name=ID;

Entity:
'entity' name=ID
Keywords '}'; Keywords

Property:


generate entity

Model:
(elements+=Type)*;

Type: Alternative

SimpleType:
'type' name=ID;

Entity:
'entity' name=ID
'}';

Property:


generate entity

Model:
(elements+=Type)*;

Type:

SimpleType:
Cardinality 'type' name=ID;
(zero or more)
Entity:
'entity' name=ID
properties+=Property* Cardinality (optional)
'}';

Property:


generate entity

Model:
(elements+=Type)*;

Type:
Unassigned SimpleType | Entity;
rulecall
SimpleType:
'type' name=ID;
Assigned rulecall
Entity:
'entity' name=ID
'}';

Property:


generate entity

Model:
(elements+=Type)*;

Type:
Multivalue
assignment SimpleType:
'type' name=ID;

Entity:
'entity' name=ID Simple assigment
'}';

Property:
type=[Type] (many?='[]')?; Boolean assigment


generate entity

Model:
(elements+=Type)*;

Type:

SimpleType:
'type' name=ID;

Entity:
'entity' name=ID
'}';
Cross reference
Property:

entity
generate entity
"http://www.xtext.org/webinar/Entity" Model

Model:
types
(elements+=Type)*;
*
Type: Type
name: EString

SimpleType:
'type' name=ID;
SimpleType Entity
Entity: extends
'entity' name=ID
properties
properties+=Property* *
'}'; Property
name: EString
type many: EBoolean
Property:

Isn‘t text a
little bit old-
fashioned?

}

protected String getErrorMessage() {
return errorMessage.toString();
}

Graphics

public boolean isSameStructure(EObject left, EObject right) {
counter = 0;
return internalIsSameStructure(left, right);
}

public boolean internalIsSameStructure(EObject left, EObject right) {
++counter;
if (!isSameClass(left.eClass(), right.eClass())) {
errorMessage.append("Classes are not equal: " + left + " != " + ri
return false;
}
List<EObject> leftChildren = getRelevantChildren(left);
List<EObject> rightChildren = getRelevantChildren(right);
if(leftChildren.size() != rightChildren.size()) {
errorMessage.append("Number of children differs " + left + " " + r
return false;
}
for (int i = 0; i < leftChildren.size(); ++i) {
if(!internalIsSameStructure(leftChildren.get(i), rightChildren.get
errorMessage.append("Children differ " + left + " " + right +
return false;
}
}

Text
return true;
}

protected boolean isSameClass(EClass left, EClass right) {
return left.getName().equals(right.getName())
&& left.getEPackage().getNsURI().equals(right.getEPackage().g
}

protected List<EObject> getRelevantChildren(EObject _this) {
List<EObject> relevantChildren = new ArrayList<EObject>(_this.eContents(
for (Iterator<EObject> i = relevantChildren.iterator(); i.hasNext();) {
EObject next = i.next();
if (!isRelevantChild(_this, next)) {
i.remove();
}
}
return relevantChildren;
}

protected boolean isRelevantChild(EObject container, EObject child) {
return true;

}

}

Graphics

counter = 0;
}

• High-level views

++counter;
return false;
}
return false;
}
return false;
}
}

Text
return true;
}

}

i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


++counter;
return false;
}
return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


• Suggests non-formalism
++counter;
return false;
}
return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


++counter;
return false;
}
return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal
i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


++counter;

• Individual tools
return false;
}
return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal
i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


++counter;

return false;
}
return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal

• Well established tools
i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


•
++counter;

Suggests non-formalism


return false;
}

• Hard to evolve

return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal

i.remove();
}
}
}

return true;

}

}

Graphics

counter = 0;
}


•
++counter;



return false;
}

• Hard to evolve

return false;
}
return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal


}

} • Easy to evolve
i.remove();

}

return true;

}

}

Graphics

counter = 0;
}


•
++counter;



return false;
}

• Hard to evolve


• Editing with mouse

}
return false;

return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal


}

i.remove();

}

return true;

}

}

Graphics

counter = 0;
}


•
++counter;



return false;
}

• Hard to evolve


• Editing with mouse

}
return false;

return false;
}
}

Text
return true;
}


}

• Detailed views

• Formal


i.remove();

•
}

} Editing with keyboard

return true;

Convention
over
Conﬁguration

Conﬁgured with
Google Guice

class MyDslRuntimeModule extends DefaultRuntimeModule {
Class<? extends ServiceInterface> bindService() {
return MyServiceImplementation.class;
}
}

Extensible Language
Generator
• Generates a lot of Java code
• Composed of fragments
• Customizable
• Add your own
fragments!

Does Xtext
integrate with
other
technologies?

Integration with EMF
eclipse

Any EMF-based modeling
Code Generator GMF Editor P R O J E C T
Component

eclipse

Component

<<abstract>>
XMIResource
Resource

eclipse

Component

<<abstract>> XMI
XMIResource
Resource

eclipse

Component

<<abstract>> XMI
XMIResource
Resource

XtextResource

eclipse

Component

<<abstract>> XMI
XMIResource
Resource

XtextResource Text

eclipse

Component

<<abstract>> XMI
XMIResource
Resource

XtextResource Text

Parser Linker Serializer

ValueConverter ScopeProvider Formatter

converging editors (Xtext and GMF)
koehnlein.blogspot.com

Questions?

ﬁnd out more at
http://www.xtext.org

Aktuelle Veranstaltungen

LOP und DSLs - Köln, 15:00
25. August 2009: Deutsches Zentrum für Luft- und Raumfahrt - Falko Riemenschneider,

NRWConf. 2009
27-28. August 2009: Wolkenburg 100, 42119 Wuppertal

Domänenspezifische Sprachen - Lars Corneliussen
12.15 Uhr - 12.45 Uhr

Die 10 Gebote der Architektur - Georg Pietrek
15.20 Uhr - 16.20 Uhr

Scrum: Vom Businessneed zum hochwertigen Produktbacklog, Bonn, 18:30
31.August 2009 - Konferenzhotel Bonn - Sebastian Neus / Dr. Martin Wrangel

Tagung: Mensch und Computer 2009, Berlin, 09:00
07. September 2009 - Leichtgewichtigkeit als Prinzip –
Gestaltung der Webanwendung myPIM durch UCD, FDD und Xtext – Torsten Krohn

Praktische Anwendung von EMF Compare, Dortmund 18:30
14. September 2009 - Harenberg City Center - Dr. Lothar Wendehals

Alle aktuellen Veranstaltungen und weiterführende Informationen auf: http://www.itemis.de/veranstaltungen

Domain-specific languages explained by expert Dr. Jan Köhnlein

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