A Domain-specific Language for the Model-driven
Construction of Advanced Web-based Dialogs
Patrick Freudenstein
1
, Martin Nussbaumer
1
, Florian Allerding
2
, Martin Gaedke
3

1
University of Karlsruhe (TH)
Institute of Telematics
D-76128 Karlsruhe, Germany
{freudenstein,
nussbaumer}@tm.uka.de
2
University of Karlsruhe (TH)
Institute of Applied Informatics and
Formal Description Methods
D-76128 Karlsruhe, Germany
florian.allerding@aifb.uni-karlsruhe.de
3
Chemnitz University of Technology
Distributed and Self-organizing
Computer Systems Group
D-09107 Chemnitz, Germany
gaedke@informatik.tu-chemnitz.de

ABSTRACT
Complex dialogs with comprehensive underlying data models are
gaining increasing importance in today’s Web applications. This
in turn accelerates the need for highly dynamic dialogs offering
guidance to the users and thus reducing cognitive overload.
Beyond that, requirements from the fields of aesthetics, Web
accessibility, platform-independence, and Web service integration
arise. To this end, we present an evolutionary, extensible
approach for the model-driven construction of advanced dialogs.
It is based on a Domain-specific Language (DSL) focusing on
simplicity and fostering collaboration with stakeholders.
Categories and Subject Descriptors
D.2.2 [Software Engineering]: Design Tools and Techniques –
User Interfaces, Evolutionary Prototyping, Petri nets. D.2.13
[Software Engineering]: Reusable Software – Domain
Engineering.
General Terms
Design, Human Factors, Languages.
Keywords
Web Engineering, User Interaction, DSL, Model-driven.
1. INTRODUCTION
Considering the significant complexity of tasks performed within
advanced enterprise Web applications as well as their
comprehensive underlying data models, highly dynamic dialogs
reducing cognitive overload and offering guidance to the users are
required. Such usability aspects have a major influence on the
efficiency and efficacy of users [2]. Beyond that, aspects from the
fields of accessibility, platform independence, and adaptivity have
to be considered. From a technical point of view, the integration
of Web service communication for retrieving updates of the
dialog’s data model or for submitting it is a common requirement
for this new generation of dialogs. Besides these application type-
specific requirements, a systematic Web Engineering approach
should also treat key factors like agility, strong stakeholder
involvement and clear business objectives arising from a project
management perspective as guiding principles [4].
Facing these requirements, we present an evolutionary, model-
driven approach for the construction of rich dialogs. The
presented Dialog DSL empowers stakeholders and domain experts
having no experience in software development to directly
contribute to the development effort by validating, adapting, and
even developing dialog models. Thus, the collaboration with
stakeholders throughout the development process can be
intensified and the possibility of misunderstandings be lowered.
2. THE DIALOG DSL
Based on our research towards DSL-based Web Engineering [3],
the Dialog DSL consists of three elements:
Firstly, the Domain-specific Model (DSM) serving as formal
schema for all dialogs that can be developed with the DSL.
Having analyzed the dialog domain, we coined the DSM as an
extensible combination of Petri net-based Interaction Structures
for describing a dialog’s dynamic behavior and XForms-based
Interaction Elements for specifying user interaction primitives.
Secondly, the Domain Interaction Model (DIM) which is strictly
based on the DSM and defines simple and intuitive graphical
notations for the concepts defined therein. Focusing on simplicity
and supplemented by a dedicated Web-based editor, it is used by
stakeholders to validate, adapt or even create dialog models.
Thirdly, the Solution Building Block (SBB) which is a dedicated
software component being capable of executing (XML-based)
dialog models by adapting its behavior accordingly.
The Dialog DSL is used in a three-phase process model in the
course of a continuous evolution. In the first phase Data Design,
the data model for the aspired dialog in terms of an XML Schema
document is either designed from scratch, extracted from a WSDL
file or retrieved from the Dialog Reuse Repository. Based on this
schema, the Dialog DSL’s technical framework is already able to
construct a running dialog. The second and third phases, Partition
Design and Appearance Design, deal with the modeling of the
dialog’s dynamic behavior and concrete appearance. With respect
to evolution, our approach allows for modifications at each stage
of the process model while preserving model consistency. All
changes can be applied at runtime and thus are visible instantly.
2.1 The Modeling Notation
The modeling notation consists of two tiers, thus fostering reuse
and separation of concerns. On the first tier, the elements from the
dialog’s data model are distributed on various partitions and
dynamic behavior between them using Interaction Structures is
modeled. Dialog partitions are represented by Petri net places
containing elements from the dialog’s data model. At runtime, if a
Petri net place is marked, its elements are visible. Petri net
transitions correspond to the performed user interaction, i.e.
changing a value in the dialog’s data model. Focusing simplicity,

Copyright is held by the author/owner(s).
WWW 2008, April 21--25, 2008, Beijing, China.
ACM 978-1-60558-085-2/08/04.

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WWW 2008 / Poster Paper April 21-25, 2008 · Beijing, China