CS 290C: Formal Models for Web Software
Lecture 11: Model Driven Development for Web
Software with WebML
Instructor: Tevfik Bultan
Model Driven Development (MDD)
• In MDD approach software development is driven by
models
– Models are written in a software modeling language
such as UML
• These high level models are systematically translated to
concrete implementations
• Models provide an abstract, implementation platform
independent view of the software system
Model Driven Development
• Software development is a modeling activity
– Even if the developers do not use any modeling
language they have mental models of the problem and
the solution they are developing
– These models are then translated to code using the
abstractions provided by the programming language
• MDD adds more layers of abstraction that can be used for
modeling both the problem domain and the solution
• Different aspects of an application can be modeled using
different modeling techniques
Separation of Concerns
• MDD promotes separation of concerns
• Different modeling techniques are used for modeling
different aspects of the application
• MDD separates technology dependant concerns from the
application logic
Automation
• MDD promotes automation
• Automated analysis and verification of models
– Since models do not contain implementation details they
are easier to analyze
• Automated code generation from models
– Guaranteeing conformance to models
• Runtime monitoring based on models
– Using runtime monitoring to make sure that the
implementation follows the behavior specified in the
model
• Automated test generation
– Models can be used to generate tests for testing the
implementation
Model Driven Architecture (MDA)
• MDA is supported by the Object Management Group
(OMG)
• MDA separates the business and application logic from the
underlying implementation platform
• MDA is a forward engineering approach where first abstract
model diagrams are developed which are later transformed
to code
• The goal of MDA is to separate the conceptual design from
the implementation architecture
The MDA approach
•
First, the developers build platform independent models
for the application
– uses machine readable design models
– uses modeling languages such as UML
• These platform independent models document the
business functionality of an application
– separate from the technology-specific code that
implements it
• After the implementation platform is chosen
– the platform independent models are translated to
platform specific models
– then the platform specific models are used to guide the
implementation for the chosen platform
Platform Independance
• The platform independent models enable the business and
technological concerns to evolve separately
• Models enable interoperability both within and across
platform boundaries
– models serve as a technology neutral specification of the
functionality
• Different components of the system can be implemented in
different platforms
– they can be easily integrated since they all conform to
the same design models
MDA Benefits for Software Lifecycle
• Implementation: MDA enables integration of new
implementation infrastructures based on the existing design
models
• Integration: Integration is easier since both the
implementation and the design models exists at the time of
integration.
• Maintenance: the availability of the design in a machinereadable form gives developers direct access to the
specification of the system, making maintenance much
simpler
• Testing and simulation: The design models can be
validated against requirements and executable models can
also be used to simulated the behavior of the system
Web Modeling Language (WebML)
• WebML is a modeling language for developing web
applications
– http://www.webml.org/
• WebML if a modeling language for MDD of web
applications
• WebML models are high-level, implementationindependent, conceptual models
WebML References
• Stefano Ceri, Piero Fraternali, Aldo Bongio: Web Modeling
Language (WebML): a modeling language for designing
Web sites. Computer Networks 33(1-6): 137-157 (2000)
• Stefano Ceri, Piero Fraternali, Maristella Matera:
Conceptual Modeling of Data-Intensive Web
Applications. IEEE Internet Computing 6(4): 20-30 (2002)
• Stefano Ceri, Marco Brambilla, Piero Fraternali: The History
of WebML Lessons Learned from 10 Years of Model-Driven
Development of Web Applications. Conceptual Modeling:
Foundations and Applications 2009: 273-292
• Stefano Ceri et al. Designing Data-Intensive Web
Applications, Morgan Kaufmann Series in Data
Management Systems.
WebML and WebRatio
• There is a spinoff company that has a software tool that
generates code from WebML models
– http://www.webratio.com/
• WebML models can be developed and translated to
implementations using a software toolsuite called WebRatio
• More than 70 companies adopted the commercial version
of the WebRatio toolsuite and used it for medium-to-large
development projects
• Separation of concerns
– Technological mapping is handled by WebRatio and
WebML models are platform independent
WebML
• WebML is used to create orthogonal conceptual models:
– Data model
• Entity-relationship diagrams (UML class diagrams),
describes the data schema
– Navigation model
• Modeling of how information is assembled to pages
and linked to each other (hypertext model)
– Presentation model
• Modeling of the views, page layout
• Separation of concerns: data content, interface logic and
presentation logic are specified separately
Data Model
• The data model is consists of entity-relationship diagrams
– similar to UML class diagrams
• Identify the data objects that will be stored in the back-end
database
– The attributes of the data objects
– The relations among the data objects
Navigation Model (Hypertext Model in WebML)
• Units for publishing content:
– Data and index units
• Links
– Navigation links
– Transport links (no navigation, just parameter passing
between units)
– Automatic links (automatically navigated)
• Contextual links transfer data whereas non-contextual links
only used for navigation
• The semantics of navigation model is based on statecharts
– There is a page navigation algorithm which given a
WebML navigation model and a user event identifies
what the contents of the next page will be
Presentation Model
• Enables dressing of the hypertext model to obtain web
pages with the desired layout and the look & feel
• It allows the use of html templates which are applied to the
hypertext model to generate the pages
• WebML includes pre-defined presentation style sheets that
can be used
Modeling skeleton
• Using WebML it is possible to abstract a web application to
elementary structures called skeletons (pairs of data and
hypertext diagrams) that show a certain aspect of the
design
• Core skeletons for displaying and managing business
objects
• Access skeletons for categorizing and selecting concepts
• Interconnection skeletons define the relations between the
business objects
• Content management skeletons