Athena Developer Guide

Athena
Chapter 13 Framework services Version/Issue: 2.0.0
13.10 Developing new services
13.10.1 The Service base class
Within Athena we use the term "Service" to refer to a class whose job is to provide a set of facilities or
utilities to be used by other components. In fact we mean more than this because a concrete service
must derive from the Service base class and thus has a certain amount of predefined behaviour; for
example it has initialize() and finalize() methods which are invoked by the application
manager at well defined times.
Figure 13.1 shows the inheritance structure for an example service called SpecificService. The
key idea is that a service should derive from the Service base class and additionally implement one
or more pure abstract classes (interfaces) such as IConcreteSvcType1 and
IConcreteSvcType2 in the figure.
Figure 13.1 Implementation of a concrete service class. Though not shown in the figure, both of the
IConcreteSvcType interfaces are derived from IInterface.
As discussed above, it is necessary to derive from the Service base class so that the concrete service
may be made accessible to other Athena components. The actual facilities provided by the service are
available via the interfaces that it provides. For example the ParticleProperties service
implements an interface which provides methods for retrieving, for example, the mass of a given
particle. In figure 13.1 the service implements two interfaces each of two methods.
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