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Designing the MOBIlearn System
of Services
he starting point of the design of the
system of services was the collection
of core scenarios, isolated from the user
requirements collected in the first project
phase. Initially, it was planned to describe
these scenarios as UML use cases.
However, this turned out to be too time
consuming, requiring too much additional
discussion (especially on the degrees of
precision and granularity required) bet-
ween those investigating the user needs
and underlying pedagogic principles and
those having to design the services.
Therefore, it was decided to proceed on
two parallel tracks.
he first track continued to collect
requirements from the end-user side
and add them to a database, maintained by
The Open University UK
( A Web interface
allowed partners to add requirements at
any time. Every so often a revision of the
database evaluates the requirements uploaded
and forwards them to the partners concerned
with implementing the respective MOBIlearn
services.This activity is important to test
the achievements of the project against the
he advantages detailed above led the
consortium to confirm the service-
based approach. At this time it was also
discussed whether the project would build
a set of Web services. Participants were
concerned about a lack of sufficient expe-
rience with the development of this kind
of service and it was agreed that the servi-
ce-based OMAF approach would imple-
ment features of Web services only as far
as they are needed for the project. For
example, there is no need for MOBIlearn
to support complex service discovery or
billing procedures, and MOBIlearn servi-
ces could be easily augmented (outside
the project) to convert them into full-fea-
tured Web services.The remaining core
parts of the development of services e.g.
establishing communication channels,
exchanging messages are sufficiently
well understood within the consortium to
proceed on a solid base.
nce relieved of the need to struggle
with coordinating interior details of
the individual services, the project
management could concentrate on the
design of the system of services.
actual user needs.The second track con-
centrated on the design of the system of
services.This was developed directly from
the selected core scenarios and it quickly
became apparent that designing software
for educational purposes requires a special
competence to translate between the
world of education and the world of soft-
ware implementation. UML diagrams
have been helpful as they depict impor-
tant features of the design under develop-
ment in an understandable, graphical way.
Different interpretations of requirements
and possibilities were resolved by intervie-
wing respective experts in the consortium.
herefore, helped by the use cases, the
implementation group broke down
the scenarios into activities. A set of servi-
ces was designed so that all specified acti-
vities could be supported.This set of ser-
vices was then structured into a number
of components so that the responsibility
for the development of the services of a
single component could be assigned to
one workpackage of the project. Each ser-
vice was augmented with a verbal des-
cription of its role and the team defined
which other services it would call.This
led to the network of dependencies
depicted in Fig. 2.
Figure 2. Services of the Mobilearn System (V1.11) Components are distinguished by colors.