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2.1 MDA
OMG’s MDA (Model Driven Architecture) (OMG,
2001a) emphasizes the use of models. This standard
defines on one hand PIMs (Platform Independent
Models) to specify business aspects independently
from the development platform, and on the other
hand PSMs (Platform Specific Models) which
describe the implementation of the I.S. on a specific
platform. The key points of this standard are model
engineering and model transformation, reducing
drastically the cost of platform changes.
2.2 RM-ODP
ISO/RM-ODP (Reference Model on Open
Distributed Processing) supplies the proper concepts
for distributed computer system specifications (ISO,
1995) (ISO, 2002). RM-ODP is based on an object
approach. The system is described from five
complementary viewpoints (IEEE, 2000) (Putman,
2001), covering as well business aspects as the most
technical aspects.
Identifying those viewpoints allows the system
specification to express at the same time but
distinctly the business the I.S. supports (Enterprise
Viewpoint), the way it is modeled in the computer
system regarding information and functions
(Information Viewpoint, computational Viewpoint,
Engineering Viewpoint) and the technical choices of
the computer system mapping user requirements
(Engineering Viewpoint, Technology Viewpoint).
The key points of RM-ODP are the sufficient
completeness of its concepts and structuring rules
and the relevance of its abstraction levels.
2.3 Why DASIBAO?
Many approaches use models to describe
information system architecture. A possible
classification identifies the approaches focused on
the notion of viewpoint, and those having detailed
the component aspects.
The first ones give a formalism or a method for the
construction of these models via the various
viewpoints. For instance, the 4+1 method (Kruchten,
1995) proposes 5 views described in UML: usecase,
logical, development, deployment and process, but
does not clarify concretely the progress between
those viewpoints. The CPL method (Bedu, 2000) is
a cube model which defines three layers (conceptual,
logical, physical), that are decomposed into domains
(activities, data, processing, technology), and more
or less automatic transitions, but the engineering
viewpoint is not really described, in particular
deployment aspects. The SAAM-ATAM method
(Kazman, 1998) proposes two viewpoints
(functional and technical) as well as the
corresponding projection. Its key point is the use of
scenarios and quality attributes, however, there
again, the engineering viewpoint is not identified.
Finally, the ODAC method (Gervais, 2002) is based
on RM-ODP viewpoints, but the steps essentially
cover the first three viewpoints.
The second group of approaches focus on the
construction of components-based architectures. For
instance, the UML Components method (Cheesman,
2001) describes how to specify a system based on
components with six activities (needs analysis,
specification, supply, assembly, test and
deployment), but the steps “needs” and
“deployment” are not completely covered. The
Catalysis method (D’Souza, 1999), as for it, covers
these six activities. Finally, Component-Oriented
Software Manufacturing method (Herzum, 2000) is
based on three components types (distributed,
business and system) within three development
processes. These methods take into account the
methodological dimension in progressing through
various viewpoints to obtain component-based
architecture, but the viewpoints they use are not
normalized.
DASIBAO method supplies the possibility not only
to identify and to assemble business or system
components, but also to follow concrete steps to
design an architecture through RM-ODP viewpoints.
The separation of platform independent viewpoints
and platform specific viewpoints, as well as the
projection between them via a repository of
solutions and architectural figures make DASIBAO
method a concrete implementation of MDA
principles.
3 DASIBAO STEPS
DASIBAO guides system architects throughout
different steps, shown on the figure 1 hereafter.
DASIBAO steps are based on RM-ODP concepts
and viewpoints, using UML notation [ISO 2003].
The concepts are usually named after the RM-ODP
standard.
SPECIFYING INFORMATION SYSTEM ARCHITECTURES WITH DASIBAO - A standard based method
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