Athena Developer Guide

Athena
Chapter 2 The framework architecture Version/Issue: 2.0.0
Chapter 2
The framework architecture
2.1 Overview
In this chapter we outline some of the main features of the Gaudi architecture. A (more) complete view
of the architecture, along with a discussion of the main design choices and the reasons for these choices
may be found in reference [1].
2.2 Why architecture?
The basic “requirement” of the physicists is a set of programs for doing event simulation,
reconstruction, visualisation, etc. and a set of tools which facilitate the writing of analysis programs.
Additionally a physicist wants something that is easy to use and (though he or she may claim otherwise)
is extremely flexible. The purpose of the Gaudi application framework is to provide software which
fulfils these requirements, but which additionally addresses a larger set of requirements, including the
use of some of the software online.
If the software is to be easy to use it must require a limited amount of learning on the part of the user. In
particular, once learned there should be no need to re-learn just because technology has moved on (you
do not need to re-take your licence every time you buy a new car). Thus one of the principal design
goals was to insulate users (physicist developers and physicist analysists) from irrelevant details such as
what software libraries we use for data I/O, or for graphics. We have done this by developing an
architecture. An architecture consists of the specification of a number of components and their
interactions with each other. A component is a “block” of software which has a well specified interface
and functionality. An interface is a collection of methods along with a statement of what each method
actually does, i.e. its functionality.
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