QUALITY OF TRANSFORMATIONS PROVIDING

INTEROPERABILITY IN SOFTWARE ARCHITECTURE

MODEL-DRIVEN DEVELOPMENT

Liliana Dobrica

Faculty of Automation and Computers, University Politehnica of Bucharest, Bucharest, Romania

Keywords: Model-driven development, Model transformations, Quality, Software architecture.

Abstract: This paper defines the quality of model to model transformations based on a set of concerns addressed by an

user and a developer. The user is a software architect that benefits of this quality during the design and

evaluation of software architecture models. Then the paper performs an analysis of the quality on a recent

approach of interoperability of tools and languages in a model-driven development environment. The key

technique used to achieve interoperability stays in the alignment of various forms of metamodels. A special

focus of discussion is on several aspects, such as the model transformation correctness, the management of

the elements possibly lost while transforming or the back propagation of changes performed in the

generated model to the original model.

1 INTRODUCTION

While Model Driven Architecture (MDA) focuses

on the generation of software implementations from

models, the same technologies can be used for other

purposes, such as transforming software architecture

(SA) model into an analysis model of a quality

attribute (Dobrica, 2011). This approach applied in

SA development is motivated by the increased

complexity of today software systems that provide

the best quality for customer satisfaction. Although

quality attributes analysis methods and techniques

exists (Clements et al., 2002); (Lassing et al., 2009)

they are not widely used because they require heavy

modeling effort throughout the development

process. To ensure that these methods and

techniques are used, they must be made accessible,

integrated into the software development process

and supported with a proper interoperability in a

tools ecosystem. Research community has

demonstrated the viability of model-to-model

transformations for design and analysis models

interchange (Dobrica et. Al., 2011) (Moreno and

Smith, 2009) (Martens et al, 2010). Interoperability

is the ability of two or several tools to exchange

information and thus to use the exchanged

information. In SA development interoperability is

required in several scenarios: architecture

refinement, architecture recovery, round-trip

engineering, tool and architecture description

language (ADL) evolution to address backward

compatibility with previous versions and, for

instance, collaborative development. Using such a

model-driven interoperable environment, an

architect should know about the provided level of

quality of a transformation.

This paper defines and analyses the quality of

model transformations from the viewpoint of

software architecture development. The paper is

organized as following. The role of the next section

is to scope the research domain. The paper continues

with the definition of quality of model

transformations. This is the main contribution of the

paper because it gathers for the first time the main

concerns addressed by a software architect, as the

main user, and a developer in specific attributes and

properties. The last section is a discussion regarding

managing the properties of transformations such that

to guarantee the required quality. It refers to the

analysis of the main attributes of quality of

transformations on a concrete example.

2 MODEL TRANSFORMATION

Model transformation is an essential operation in

model-driven engineering (MDE). Model

transformations are always based on a metamodel. A

305

Dobrica L..

QUALITY OF TRANSFORMATIONS PROVIDING INTEROPERABILITY IN SOFTWARE ARCHITECTURE MODEL-DRIVEN DEVELOPMENT.

DOI: 10.5220/0003613303050308

In Proceedings of the 6th International Conference on Software and Database Technologies (ICSOFT-2011), pages 305-308

ISBN: 978-989-8425-77-5

 2011 SCITEPRESS (Science and Technology Publications, Lda.)

model-to-model transformation creates another

model, which is typically based on a different

metamodel than source model (Czarneki and Helsen,

2006). Such transformations generally describe how

the constructs of the source metamodel are mapped

on the constructs of the target metamodel. Both the

source and target of a model transformation are a set

of models. The Query/View/Transformation (QVT)

specification (OMG, 2005) is the solution for model

transformations in the OMG modeling framework.

There are many other model transformation

languages emerging from industrial and academic

efforts (Didonet et al., 2006). As a consequence,

there is an increasing number of model

transformations that are being developed for

different applications domains and therefore

software modelers should be able to compare and

select the languages and tools for their particular

problem. It should be noticed that a model

transformation is also considered a model (Bezivin

et al., 2006). Just as a model can be created,

modified, and augmented through a transformation,

a transformation can be regarded as a model, and

therefore, it can itself be instanced or modified.

Higher order transformations (HOT) represent a

solution of obtaining automatically model-level

transformations by taking other transformations as

input and producing other transformations as output.

Series of model-to-model transformations that

enable information migration among models are

used to define a transformation system. Weaving

models form the logic that generates

transformations. A number of methods to specify

and construct weaving models are currently being

developed. Conceptually weaving models conform

to a given weaving metamodel and they can be

defined either manually or by scripting languages.

A number of interesting tools, most of them open

source are available today. These tools may be used

to automate model transformations. Many

technologies are emerging in the context of Eclipse

platform. Some of the most important are Eclipse

Modelling Framework (EMF) and Generative Model

Transformer (GMT). GMT is a container of projects

and AtlanMod Transformation Language (ATL) is

part of it. ATL is a model-to-model transformation

engine that has matured over the past several years

(Jouault and Kurtev, 2006

). ATL is QVT compliant.

An ATL transformation is specified as a set of

transformation rules. In ATL rule inheritance is a

mechanism that makes the transformation code more

compact and it shows clearly what is common and

what is specific in the transformation of similar

elements. ATL is part of the platform called

AtlanMod Model Management Architecture

(AMMA), which contains various tools for the

creation of domain specific languages. Among these

tools, AMW is the platform that manages weaving

models. A weaving model conforms to an extensible

weaving metamodel. The weaving models are

defined by the XML Metadata Interchange (XMI).

3 TRANSFORMATION QUALITY

The quality of a transformation is defined

considering various concerns addressed by an user

and a developer. In our view, the user is a software

architect that benefits of such a tools ecosystem

during design and evaluation of software

architecture models. The developer is another

stakeholder, who has a specific viewpoint regarding

a development process (Rozanski and Woods,

2005). Thus, the quality of a transformation is

defined as a complex of specific characteristics that

include the startup effort, transformation mainte-

nance, traceability, invertibility and correctness of a

transformation (Cortelessa et al., 2008). Futhermore,

when dealing with multiple transformations of

different models important is lost in translation

property. The startup effort represents the startup

time in using a transformation language tool. In

addition, with transformation languages it is

necessary to formally define and maintain source

and target metamodels. Transformation maintenance

concerns the evolution in time of a transformation.

This means that a transformation has to be

maintained by adding/removing/changing transfor-

mation rules. Traceability is the ability to trace back

elements of the target model to elements of the

source model. Invertibility is defined as the ability to

automatically build the inverse transformation.

Traceability and invertibility are the main attributes

of concern in round-trip engineering (RTE). Two

models are synchronized with respect to a

transformation if the relevant part of the target

model can be created by applying the transformation

to the source model. Another main issue regarding

transformation is to verify the correctness of a

transformation, in fact how to guarantee that the

output model is consistent with the source model.

This opens the possibility to build formal proofs of

transformation correctness (Bordin and. Vardanega ,

2007). Correctness of a transformation is divided

into syntactic correctness and semantic correctness.

Syntactic correctness should answer to the following

question: Given a well-formed source model, can be

guaranteed that the target model produced by the

ICSOFT 2011 - 6th International Conference on Software and Data Technologies

306

transformation is well-formed? A guarantee of

syntactic correctness is the presence of mechanisms

to check if a model conforms to its metamodel.

Semantic correctness should answer the following

question: Does the produced target model have the

expected semantic properties? It can be exactly

defined by what kind of properties should be

satisfied through model transformation.

In multiple transformations of different models,

the models should be kept aligned and consistent.

One of the most important properties to preserve is

when changes made on the generated model must be

propagated back to the others. Various approaches

have been recently proposed in order to tackle this

problem. In (Hettel et al., 2008) the authors provide

a framework to compare current model

synchronization approaches, classifying them by the

nature of the involved transformations (i.e., whether

they are total or partial, bijective or injective, and if

the reverse transformations are given or not). All of

these approaches can be exploited depending on the

assumptions made on the transformations generated

from the weaving models. For example, assuming

that the generated transformations are total and

bijective, then the corresponding approach may be

used. This implies that an analysis of the generated

transformations should be performed and

assumptions on them should be considered. When

this solution is not possible to be applied (e.g.,

transformations with many manual ad hoc

refinements are hard to classify) a basic and generic

mechanism to keep models consistent is devised in

(Malavolta et al., 2010).

4 ANALYSIS OF QUALITY IN

MODEL TRANSFORMATIONS

DUALLy is a framework to create interoperability

among ADLs based on a specific star topology

(Malavolta et al., 2010). In the centre of the star is

the semantic core set of modelling elements. The

transformation system is made of a series of low-

level model-to-model transformations that enable

information migration among model instances.

These transformations are constructed automatically

executing HOTs (Figure 1). From a technological

viewpoint DUALLy is engineered as an extension of

an open source platform that manages weaving

models. Extension consists of an editor, a weaving

metamodel and a set of HOTs. The main advantages

that DUALLy provides are compliance with OMG

standards and interoperability with other modelling

tools. DUALLy achieves independence from tools

used for modeling or analysing SAs. DUALLy

provides a good level of scalability since software

architects do not need to trace models while round-

tripping DUALLy-zed models. The correspondence

between model elements is identified by directly

referring to an identification attribute. The weaving

models form the logic that generates ATL

transformations. While the ATL transformations

generation phase can be the most crucial, the

framework makes it totally transparent to the

software architect that does not need any knowledge

about model transformations.

model

MM 2

MM1

semantic mm

link

emantic mm

link

con forms to

conforms to

aut omatic

transf .

automatic

transf.

Level

m2m

transf.

m2m

transf .

MMM

Level

HOT

weaving

mm.

weaving

mm.

Tool 1

(Design

Tool)

Tool 2

(Analysis

Tool)

Figure 1: DUALLY Model Transformations.

The startup effort for DUALLY is high because

transformations are implemented in ATL and KM3

language, which is are young languages and

developers have poor experience in using them.

Transformation maintenance is simple because

DUALLY is implemented in ATL, which is a

transformation language supported by tools that

automatically manage many aspects of maintenance.

Traceability and invertibility are also satisfied

because of ATL language, which is formally defined

and openness the possibility to build formal proofs

of transformation correctness. Thus it raises in this

way the level of trustability of the transformation.

DUALLY provides and demonstrates the

correctness of transformations. It analysis corre-

ctness problems on bidirectional transformations and

identifies conditions that disambiguate a possible

non-determinism.

Lost in translation with DUALLy is handled with

a specific mechanism. This mechanism stores un-

matched elements in a model conforming to the lost-

in-translation metamodel in order to properly

redeploy them in the proper diagram, when moving

back to the originating technology. This mechanism

provides the means to automatically store and read

those lost elements when closing the round-trip

journey. The generated direct transformation is

instructed so that it returns as output a target model

QUALITY OF TRANSFORMATIONS PROVIDING INTEROPERABILITY IN SOFTWARE ARCHITECTURE

MODEL-DRIVEN DEVELOPMENT

307

and an additional model containing the lost-in-

translation elements. Reverse transformation takes

as input the changed generated model and a

previously created lost-in-translation model and

reads its elements to the originating model. When

executing a HOT, kinds of transformations are

possible. Among these, it can be mentioned not

instructed, when the model transformation does not

take into consideration the lost-in-translation

mechanism and instructed, when the transformation

creates the additional lost-in-translation model and

adds its elements to a target model.

5 CONCLUSIONS

This paper has defined the concept of quality of

model-to-model transformations based on a set of

concerns addressed by an user and a developer.

Because model-driven environment is the current

trend in software architecture design and analysis, a

key user, who is the principal beneficiary of such a

tools ecosystem, is the software architect. The

developer is also an important stakeholder

addressing various concerns regarding quality during

development and evolution of such an approach.

Then the paper has performed an analysis of the

quality on a recent approach of interoperability of

tools and languages in a model-driven development

environment. The description of this approach has

revealed that the key technique used to achieve

interoperability stayed in the alignment of various

forms of metamodels. A special focus of discussion

was on several properties, such as the model

transformation correctness, the management of the

elements possibly lost while transforming or the

back propagation of changes performed in the

generated model to the original model.

Because this paper has described work in

progress, much remains to be done to refine the

definition given here. This definition will be used in

other evaluations and we’ll try to develop metrics

for analysing quantitatively this quality of model-to-

model transformations. The final goal of the future

work is an ontological definition to be integrated in a

knowledge management system.

ACKNOWLEDGEMENTS

This work was supported by Romanian research

grant CNCSIS –UEFISCSU, project number PNII –

IDEI 1238/2008.

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