Model Transformations for Hypertext modeling on Web
Information Systems
Paloma Cáceres, Valeria de Castro, Juan M. Vara, Esperanza Marcos
Rey Juan Carlos University
{paloma.caceres, valeria.decastro, juanmanuel.vara, esperanza.marcos}@urjc.es

ABSTRACT
In response to the lack of suitable methods to build the navigation
model of Web Information Systems (WIS), we presented in past
works HM
3
, the Hypertext Modeling Method of MIDAS, a
methodological framework for the agile development of WIS. We
proposed a method to obtain the navigation model of a WIS,
starting from the conceptual data model and the user
requirements, collected in the use case model. In this work,
continuing with the MDA approach for WIS development that we
are following with HM
3
, we define the model to model
transformations needed at the PIM level to get the hypertext
model from the behavioral and content models. Firstly we specify
the transformation rules with natural language to later map them
to graph transformation rules.
Keywords
Model Transformation, Hypertext/Hypermedia, User Issues,
Modeling Methodologies.
1. INTRODUCTION
Despite the differences found between the traditional
methodologies for Web Information Systems development, all
they follow a similar approach to obtain the navigational model:
they start from the conceptual model [8] [9]. In previous works
and in response to certain lacks suffered by this structural
approach, we proposed to address the problem of the systematic
construction of the navigation model from a user services
oriented perspective [4] [7]. That is, we mainly take into account
the services required by the user, what we call conceptual user
services. This way, we proposed the Hypertext Modeling Method
of MIDAS (HM
3
): a method to obtain the navigation model
starting from the user services model, a use case model in which
we identify conceptual user services as stereotyped use cases. In
HM
3
we also take into account the conceptual data model, but just
in a second step, to complete the information collected in the
output model.
The proposed method includes the process, the models and the
mappings between them. As the mentioned previous works show,
the mappings between the models play a very important role,
given that the method is based on a continuous development
process in which, according to the Model Driven Architecture
(MDA) principles [10], the models act as the prime actors. Each
step of this process consists basically in the generation of an
output model starting from one or more input models on which
the mapping rules are applied. In the remaining steps of the
process, this output model acts as one of the input models.
In this work, we complete the definition of HM
3
by specifying a
graph transformation approach to effectively realize the mappings
defined in HM
3
. The term “Graph Transformation” is used to
refer to a special kind of rule-based transformations that are
typically represented diagrammatically [20]. So, given that we
define the HM
3
mapping rules in a rule-based manner, it seems
properly to use a graph transformation approach to later formalize
them.
HM
3
is part of MIDAS, a model driven methodology for agile
development of WIS. MIDAS proposes to model the WIS
according to three basic aspects: hypertext, content and behavior.
This work focuses on the MIDAS method to model the hypertext
aspect whose final output is the navigation model, obtained by
means of the model to model transformations at PIM level
presented in this work.
2. THE FRAMEWORK AND THE
PROCESS
In this section we summarize the main characteristics of the MDA
framework at which this work is located and the modeling process
that is completed with the model to model transformations
specified in this work.
2.1 MIDAS Framework
MIDAS is a methodological framework for agile development of
WIS, which proposes a Model Driven Architecture [5] based on
the MDA proposed by the Object Management Group (OMG)
[10]. MIDAS proposes to model the WIS according to two
orthogonal dimensions (see Figure 1).
BEHAVIORHIPERTEXTCONTENT
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P
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Conceptual
Data Model
User Services
Model
Extended
Navigation Model
Extended
Use Cases Model
Extended
Slice Model
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XML Schema
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Xlink
Model
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Model
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Figure 1. Model Driven Architecture of MIDAS.

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On the one hand, MIDAS proposes to model the WIS taking into
account the platform dependence degree (based on the MDA
approach): firstly, specifying the whole system by Computation
Independent Models (CIMs), Platform Independent Models
(PIMs) and Platform Specific Models (PSMs); and secondly,
specifying the mapping rules between these models. On the other
hand, MIDAS proposes to model the WIS according to three basic
aspects [11]: hypertext, content and behavior. Besides, MIDAS
suggests using the Unified Model Language (UML) as unique
notation to model the whole system, as well as the use of UML
profiles (or the definition of new UML profiles) to model aspects
not covered in the UML standard [12][13][23].
As mentioned previously, in this work we focus on the
transformations between the PIM models that were introduced in
[4], involved in the modeling of the hypertext aspect of a WIS.
2.2 The Hypertext Modeling Method of
MIDAS
The Hypertext Modeling Method of MIDAS (HM
3
) [4], [7] is
defined from a user services oriented perspective, that is, taking
into account the services required by the users of the WIS. The
inputs of the method in the HM
3
process are the user
requirements and the conceptual data model; the output is the
extended navigation model.
As can be shown in Figure 2(a), the process includes three new
intermediate models to finally obtain the extended navigation
model: the user services model, the extended user services model
and the extended slices model. Besides, an Activity Diagram is
used to model the use services composition and to obtain the route
that will guide the user on his navigation through the WIS.
The HM
3
process is an iterative and incremental process that
sometimes requires the decision making by the system designer.
To clarify this decision making, we have captured the whole
process in the activity diagram showed in Figure 2(b). In this
figure, we have identified the different tasks associated with each
one of the steps, that is to say, with the generation of the different
models. As showed in Figure 2(a) and Figure 2(b), the output of
each one of the steps composing the process is a new model: user
services model, extended use case model, extended slice model
and extended navigation model.
This way, we have defined the process as the set of activities
needed to generate each one of these models. By means of simple
tasks to do over the input models, the respective output model is
generated for each step. It becomes obvious that these tasks are no
more than the set of mappings between models that must be
carried out for each step of the process.

Extended Navigation Model
User Service Model
User Requirements
Conceptual User Services
Extended Slice Model
Structural and Functional Basic Services
Navigational Structures
Activity Diagram
Conceptual Data Model
Attributes Routes
Extended Use Case Model
Extended
User Services Model
Generation
User Services Model
Generation
Identify
one
SIW Actor
Identify
one
User Service
Represent
the
User Services Model
[SetOf.Actors
!= empty ()]
[SetOf.UserServices
!= empty ()]
Split
a
User Service
Split the Composite
Use Service
[isComposed]
Stereotype as
Functional
or Structural
[isBasic]
[SetOf.UseServices
!= empty ()]
Select
one
Use Service
Define include
and extend
associations
Activity Diagram
(AD) for
the User Service
[SetOf.UserServices
!= empty ()]
Represent
Extended
User Services Model
Realizar el
diagrama de
clases
Select one
User Service
Assign attributes
for each slice
Fix the slices
sequence
according to the AD
Turn the
<<SBS>>
into <<SS>>
Appoint the
route associated
to the User Service
Turn the
<<FBS>>
into <<FS>>
Identify subroute
for each
fork at the AD
[SetOf.UserServices
!= empty ()]
Represent
Exended Slices Model
Extended Navigation Model
Generation
Add Initial Menu
Add new Menu
[SetOf.Branchs
!= empty ()]
Add Index or Query
[SetOf.StructuralSlices
!= empty ()]
Extended Slices Model
Generation

Figure 2. a) HM
3
process summary and b) HM
3
process detailed

2.3 UML Profile for Hypertext Modeling
As well as HM
3
needs to represent UML elements with new
semantics associated, we have extended the UML metamodel by
defining a new profile (a package containing model elements that
have been customized for a specific domain or purpose using
extension mechanisms, such as stereotypes, tagged definitions and
constraints). The set of stereotypes used to define the profile, and
the relative UML metaclass extended by each one can be found
on Table 1, while the graphical presentation of these stereotypes
is showed in Figure 3. This new UML extension is collected in
the definition of four metamodels, one corresponding to each one
of the new models introduced in HM
3
: User Services metamodel,
Extended User Services metamodel, Extended Slices metamodel
and Extended Navigational metamodel, and the restrictions over
these metamodels defined with the OCL standard.
These metamodels are presented in Figure 4 with dashed lines
pointing out the new elements added in each one.
In next subsections we will give just a brief overview of each one
of these metamodels. For an in-depth explanation on the
semantics associated of anyone of the new elements included in
the different metamodels, the reader is referred to [4] and [7].
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