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Semantic Web Services 175
for such information he is interested in. SemanticLog is used for logging different events
occurring during user interaction with JOP. JDBSearch is a full text indexer and allows
querying to search in the information space. Each of these tools is integrated in the Cocoon
and thus deployed on the server where Cocoon is running (see Figure 6-6). This means that
they are centralized into one execution point.
Physical server
Cocoon
Browser
HTTP
HTTP
JOP
Factic
JDBSearch
SemanticLog
Figure 6-6. Classic job offer portal.
If JOP is build using SOA concepts, web services wrap application parts of various granularity.
It is not enough to just transform some of them to web services. If an application uses
web services it still does not mean that it is SOA based. Also other concepts must be applied.
This includes for example the use of enterprise service bus (provides a messaging bus and
content-based routing between service providers and consumers) and distribution of the
services. Those parts of JOP which can be built as web services can be whole modules, tools
or only some methods offered by tools. For example each module in the boxes from Figure
6-5 can be transformed into a web service. We have mentioned that JOP is built using the
pipes and filters architectural patterns. Here, we have a chain of processing elements where
the output of an element is the input of the next. Each element performs some processing of
the input data resulting in output data. When moving to SOA, each of these elements should
be realized as web service.
The benefits of web services include the possibility of use the wrapped elements not only
from the user interface of JOP but also programmatically by other applications. For example
in the case of Factic, we can wrap the method which cut of the information space based
on given facets. Similarly, JDBSearch searching method can be used via web service call.
Transforming the logging method of SemanticLog into web service brings the possibility
of calling it also from other systems. This way, user activities not only from JOP can be
gathered. Also other systems the user is working with can effectively log the events. After
this, by analyzing the logs, we can obtain much more information about the user than if only
those activities realized in JOP are captured. This results in richer user model and better
personalization. If the mentioned methods are wrapped as web services, their execution
does not need to be performed on the same physical server the JOP is running on (see
Figure 6-7). Hence, distribution of the execution may take place. This is required when
higher computation power is in demand.