![](bg3.png)
placed. The site hierarchy should correspond to the
network architecture depicted in Physical View,
while process and user profiles are related to nodes
included in Physical View.
An example of Topology View is shown in figure
2. This example illustrates the University of Athens
and its schools. Sites are depicted through trapezium
icons. According to figure 2, School of Science,
comprises a Science Library and a Science Lab.
Science Lab, for instance, includes the Science
Student Profile and a client process, namely Search
Science Library. The former is illustrated using the
UML actor icon while the latter using the small
cogwheel icon. The large cogwheel denotes a server
process (e.g. Local Database Server). The notation
used for the connections between sites and processes
or user profiles is the membership notation
introduced in UML 2.0. Lastly, figure 2 shows also
the interaction among processes and user profiles
through the dashed lines. These interactions are in
compliance with the interactions among modules
included in the respective Application View, as
processes of Topology View correspond to modules
of Application View.
4 UML EXTENSIONS
All stereotypes that constitute the Distributed
System Configuration Profile are listed in appendix
A, along with the base class they derive from, their
attributes and constraints. As stated implicitly by the
Application View table, the representation of the
external and internal parts of Application View are
based on use cases and activity diagrams
respectively. Use cases in UML are means for
specifying system functionality. As such, they are
suitable for the representation of services, since each
service corresponds to specific functionality offered
by the relative system module. Modelling services as
use cases and the owning modules as packages, we
have used UML in a valid and consistent manner in
order to produce a functional and descriptive model
for our purposes. Indeed, the relation among services
can be pertinently modelled using the Include
relationship defined in UML between use cases.
This relationship means that the base use case is not
complete in itself but dependent on the included use
case (OMG, 2004) similarly as between services in
Application View. Also, the behaviour of a use case
can be described through interaction, activity or state
machine diagrams. We used this feature by adopting
activity diagrams to illustrate the implementation of
a service. Since a service implementation involves
flow of operations, the eligibility of activity
diagrams for its representation is obvious.
As far as Operation Dictionary is concerned,
since it involves interactions between operations
showing in particular invocation order and
parameter passing between them, its representation
is facilitated by the UML communication diagrams
which focus on the interaction between entities.
Lastly, the representation of Topology View is
based on UML component diagrams, because in this
view, system modules are not examined in terms of
their services but they are considered as pieces of
software which must be installed at specific atomic
sites. Furthermore, taking into consideration that
Physical View is modelled by deployment diagrams,
adopting component diagrams for the representation
of Topology View facilitates mapping between the
two views, since the relationship between node and
component model entities are already supported in
the core UML metamodel. As a result, site range can
be mapped onto network range, enabling thus the
identification of dependencies between application
configuration and network topology.
REFERENCES
IBM Co, 2005. Introducing Rational Software Modeler,
http://www-128.ibm.com/developerworks/rational/
library/05/329_kunal/
Kaehkipuro P., 2001. “UML-Based Performance
Modeling Framework for Component-Based
Distributed Systems”, Lecture Notes in Computer
Science 2047, Performance Engineering, Springer-
Verlag.
Nikolaidou M., D. Anagnostopoulos, 2005. “A Systematic
Approach for Configuring Web-Based Information
Systems”, Distributed and Parallel Database Journal,
Vol 17, pp 267-290, Springer Science.
OMG Inc, 2004. UML Superstructure Specification,
Version 2.0, 8/10/2004.
Savino-Vázquez N.N. et al., 2000. “Predicting the
behaviour of three-tiered applications: dealing with
distributed-object technology and databases”,
Performance Evaluation Vol. 39, no 1-4, Elsevier
Press.
Figure 2: An example of Topology View.
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