Conceptual Roadmap

First, it may be interesting to briefly discuss what is the purpose of coming up with a domain metamodel. As a matter of fact, the main reason and advantage of working on a domain metamodel is the same as the reason for working on a system model: come up with a simplified representation of the domain that helps its understanding and usability. The domain metamodel can then be instantiated to model different systems related to the domain and therefore build a set of related applications.

Note also that when building an application framework we are also in some way trying to come up with a (practical) domain metamodel. We are in fact trying to find a simplified representation of the domain that can be used to easily construct new applications related with that domain. A framework does not only give a set of tools that can be used as building pieces (black-box framework) but also a conceptual interpretation of the domain (white-box framework) (see 1.3.3). One way to see the process of building a framework is that we must first have to come up with a domain model and then implement it. Nevertheless, if we adopt a more incremental or ``agile'' point of view, we are able to see it the other way around: when we start building the framework we may have a vague idea of the domain model or metaphor but it is the process of designing the framework that actually ends-up defining the model. All these issues will be contextualized and further developed in chapter 1.

This thesis presents an object-oriented metamodel for signal processing that will be called Digital Signal Processing Object-Oriented Metamodel, DSPOOM for short. DSPOOM is a metamodel that, as it will be proven throughout this work, can be used to effectively translate any digital signal processing system into the software domain. This modeling is accomplished through the use of the object oriented paradigm and, in doing so, we gain more understanding - and thus control - of the different actors and forces present in the original system.

After this introduction, in chapter 1 we will review the basic foundational concepts upon which the thesis is built. Departing from the initial glossary this chapter will focus on establishing a solid ground by clearly defining the main axis: the concept of model, the object oriented paradigm and associated techniques and uses, and a review of different models that have been traditionally been used for modeling signal processing or digital communication systems. In this chapter we will also discuss on issues such as frameworks, models and metamodels. A somehow more extensive review is given of software engineering techniques as the readers are not expected to be experts in the software engineering domain.

Chapter 2 presents thorough review of software environments for audio and music processing. Each of them responds to a different rationale, focus and general model. The analysis of these tools is a vital task for understanding the domain in which this thesis is built. Many of these environments also represent clear predecessors, not only of the framework that will be presented in the following chapter but also of the different conceptual models and metamodels that are later derived.

In next chapter, number 3, the CLAM framework for developing audio and music applications is presented. CLAM is at the same time a proof of concept and the generating seed of the model presented in this Thesis and commented in the next chapter. As a matter of fact, implicit to this thesis is the idea that frameworks generate models, and not the other way around (see 1.3.5).

In chapter 4 the main issues and concepts that form DSPOOM are discussed. The central part of this chapter is devoted to explaining a classification of digital signal processing objects that may be used to model a system.

In chapter 5 we defend that the model presented, and the framework that realizes it, can be effectively used for working with new paradigms that go beyond the classical signal processing framework. More precisely, DSPOOM is shown to be useful as the basis for a content processing or semantic framework.

In chapter 6 we finish the excursion up the abstraction ladder and end up presenting an object oriented model for music (i.e. symbolic) processing. It is not the first time that music and objects meet, but here we discuss how the model is related to the one presented for the lower signal level and can use many tools included in the CLAM framework.

Finally, in chapter 6.5 we draw some conclusions and envision some future work that could be used to broaden the scope of this Thesis.