A large part of this work is about concepts and definitions. All of them will be thoroughly defined and commented in the corresponding sections. Nevertheless, and in order to establish a common glossary and start stating a point of view, it is interesting to first give a short definition of some terms.
Object:Physical or abstract entity that can be conceptually isolated due to its high cohesion and low coupling with other entities.
Class: A set of related objects with the same behaviour and internal structure.
System: We will see throughout this thesis how the word system has slightly different meanings and interpretations depending on the context. However, we will accept as a sufficiently generic definition, the one given by the Institute of Electrical and Electronical Engineerings professional group in System Science and Cybernetics when they state that a system is `` a large collection of interacting functional units that together achieve a defined purpose'' [Rowe, 1965].
Model: A model can be understood as the formal abstract representation of a given system. A single system can be represented through different models, depending on the level of abstraction required and foreseen use.
Metamodel: A model that explains a set of related models.
Paradigm: The most commonly accepted definition of paradigm is that of Thomas Kuhn who describes a paradigm as the set of common beliefs and agreements shared between scientists about how problems should be understood and addressed [Kuhn, 1962].
Framework: A framework (in the Software Engineering domain) is an abstract design of a set of related applications in a particular domain. This abstraction can be then instantiated to build a concrete application.
Metaphor: According to [Beck, 2002], a metaphor is the linking of two sets of concepts so one set of concepts is understood in terms of another.
Signal: A function of one or more independent variables that contains information about the behavior or structure of a given phenomena [Openheim and Willsky, 1997].
All these concepts and the way they relate will be further explained and discussed and will build the conceptual framework upon which this thesis is based. But as a first introduction it may be well worth to add a few considerations that can already help better understand the above given definitions and the way they conceptually relate.