1. © Software Languages Team, University of Koblenz-Landau
Modeling software systems
at a macroscopic scale
Ralf Lämmel
Software Languages Team
University of Koblenz-Landau, Germany
Joint work with Jean-Marie Favre, Andrei Varanovich, andVadim Zaytsev
https://github.com/avaranovich/megal
http://softlang.uni-koblenz.de/mega

2. © Software Languages Team, University of Koblenz-Landau
Source: Colin Atkinson, Thomas Kühne:
Model-Driven Development: A
Metamodeling Foundation. IEEE Software
(SOFTWARE) 20(5):36-41 (2003)
Who is Lassie?
What’s wrong with
*modeling?

3. © Software Languages Team, University of Koblenz-Landau
http://en.wikipedia.org/wiki/Lassie
http://www.counter-currents.com/wp-content/uploads/2011/10/Lassie.jpg
Too many implicit assumptions!

4. © Software Languages Team, University of Koblenz-Landau
A typical software project
(at the macroscopic scale)
programming languages
(e.g., Java, PHP, JavaScript, or Python)
DSLs (e.g., CSS, XSLT, or SQL)
library-based languages
(e.g., JQuery, DOM API)
configuration languages
(e.g., Hibernate mapping)
models
schemas
models
“many” languages and technologies
“somehow” related

5. © Software Languages Team, University of Koblenz-Landau
Can we model software projects more precisely
in terms of languages,
technologies,
and concepts?

6. © Software Languages Team, University of Koblenz-Landau
A megamodel is a model of which at least
some elements represent and/or refer to models
or metamodels.
Source: Bezivin, J., Jouault, F.,Valduriez, P.: On the need for
Megamodels. In: Proceedings of the OOPSLA/GPCE: Best Practices
for Model-Driven Software Development workshop (2004)
We embrace this notion in the broadest sense:
programs are models and grammars are
metamodels (or v.v.) etc.

7. © Software Languages Team, University of Koblenz-Landau
A megamodel
!
ATL Starter’s Guide Date 07/1
MMM
MMt
Ma Mb
MMa
Mt
MMb
conformsTo
conformsTo conformsTo
conformsTo
conformsTo
conformsTo
Transformation
MMMMMM
MMtMMt
MaMa MbMb
MMaMMa
MtMt
MMbMMb
conformsTo
conformsTo conformsTo
conformsTo
conformsTo
conformsTo
Transformation
Figure 1. An overview of model transformation
1 summarizes the full model transformation process. A model Ma, conforming to a metamo
s here transformed into a model Mb that conforms to a metamodel MMb. The transformation
d by the model transformation model Mt which itself conforms to a model transformat
odel MMt. This last metamodel, along with the MMa and MMb metamodels, has to conform t
etamodel (such as MOF or Ecore).
Source:
http://wiki.eclipse.org/ATL/Concepts#Model_Transformation
Model
transformations
with ATL
What to think
of this part?

8. © Software Languages Team, University of Koblenz-Landau
A megamodel
Source:
http://en.wikipedia.org/wiki/Tombstone_diagram
Bootstrapping a C compiler written in C, by compiling
it using another compiler written in machine code.

9. © Software Languages Team, University of Koblenz-Landau
• Megamodeling must help with managing diversity
and heterogeneity of software technologies.
• Cognitive value is important!
Specific motivations of megamodeling:
Empirical Assessment of MDE in Industry
by John Hutchinson, Jon Whittle, Mark
Rouncefield and Steinar Kristoffersen
use of models for team communication
use of models for understanding a problem
at an abstract level
use of models to capture and document
designs
“Generic” motivations:

10. © Software Languages Team, University of Koblenz-Landau
The notion of megamodel
• Megamodels are (ER) models.
• Entities of interest
‣ Languages
‣ Technologies (components thereof)
‣ Programs
‣ ...
• Relationships of interest
‣ Conformance
‣ Transformation
‣ ...

11. © Software Languages Team, University of Koblenz-Landau
How to validate megamodeling claims?
By “=” we mean (roughly) that one can define the same
set of instances up to a uniquely defined isomorphism.
=
?

12. © Software Languages Team, University of Koblenz-Landau
Fig. 1. The linguistic architecture of a software product when displayed with the Me-
gaL/Explorer tool.
Demo
http://worker.101companies.org/MegaModels/implementations/xsdClasses/

13. © Software Languages Team, University of Koblenz-Landau
Linked megamodels
An entity is linked
to a unique
resource that
can be browsed
and examined
correspondsTo

14. © Software Languages Team, University of Koblenz-Landau
<xs:element name="company">
<xs:complexType>
<xs:sequence>
<xs:element ref="name"/>
<xs:element maxOccurs="unbounded" minOccurs="0" ref="department"/>
</xs:sequence>
</xs:complexType>
</xs:element>
http://101companies.org/resources/contributions/jaxbComposition/inputs/
Company.xsd/element/xs:schema/element/xs:element?format=html
http://101companies.org/resources/contributions/jaxbComposition/src/main/java/
org/softlang/company/xjc/Company.java/class/Company?format=html
public class Company {
@XmlElement(required = true)
protected String name;
protected List<Department> department;
/**
* Gets the value of the name property.
*
* @return
* possible object is
* {@link String }
*
*/
public String getName() {
return name;
}
.....
Use of fragments to establish
an observable correspondence

15. © Software Languages Team, University of Koblenz-Landau
Key design principles of MegaL as
general-purpose megamodeling language
• Entities and relationships are extensible.
• Everything is a resource, i.e.:
• accessible over HTTP.
• Relationships are executable.

16. © Software Languages Team, University of Koblenz-Landau
MegaL prelude
// Entity types
Set < Entity .
Artifact < Entity .
Language < Set .
Technology < Entity .
Concept < Entity .
File < Artifact .
Folder < Artifact .
// Relationship types
elementOf < Entity * Set .
subsetOf < Set * Set .
partOf < Artifact * Artifact .
instanceOf < Concept * Concept .
isA < Concept * Concept .
conformsTo < Artifact * Artifact .
definitionOf < Artifact * Language .

17. © Software Languages Team, University of Koblenz-Landau
Some megamodels
Java : Language .
extern JavaProgram : File .
JavaProgram elementOf Java .
/* Models, metamodels, and conformance */
Model < Artifact .
Metamodel < Model .
conformsTo < Model * Metamodel .
/*
The MVC concept.
MVC consists of model, view, and controller.
Those subconcepts depend on the main concept.
MVC is a design pattern.
*/
MVC : Concept .
Model @ MVC : Concept .
View @ MVC : Concept .
Controller @ MVC : Concept .
DP ["Design pattern"] : Concept .
Model partOf MVC .
View partOf MVC .
Controller partOf MVC .
MVC instanceOf DP .

18. © Software Languages Team, University of Koblenz-Landau
• Different sources of (partial) errors
• Extensibility of the language
• To be controlled by the type system
Design challenges of MegaL

19. © Software Languages Team, University of Koblenz-Landau
MegaL pipeline
event recorder
event bus
events events events
report

20. © Software Languages Team, University of Koblenz-Landau
Thank you!
Questions?
https://github.com/avaranovich/megal
http://softlang.uni-koblenz.de/mega