2 Concept of the labAlive Toolbox

From a precise point of view, the labAlive toolbox consists of two parts:

• An abstract concept of (abstract) classes serving as a formal representation of any kind of system that consists of `blocks' and `connections' of blocks.
• Dedicated implementations of these abstract classes for the needs of system theory and communications lectures, i.e.\ implementing linear and non-linear systems, FIR and IIR filters, frequently used sources, and a useful set of signal visualization tools like oscilloscopes and eye pattern diagrams.

Natural, easy to understand mappings between the familiar theoretical description of the systems to be demonstrated and the architecture of the abstract base classes on the one hand, and between the abstract base classes and a concrete implementation on the other hand, were recognized as vital for successful development and later application of the toolkit.

The latter mapping is provided by the inheritance mechanism of Java in a very intuitive way--a more specialized filter simply extends a general FIR filter, which extends an analog, discrete-time system, which finally extends a system, which extends the base component of all labAlive classes.

The former mapping turned out to be more difficult to solve and will be explained in more detail in section 3. The two most important characteristics of the abstract concepts are firstly, that the fundamental difference between connections and blocks is already reflected at the second lowest inheritance level, and secondly, that a set of connected blocks (a system) can be seen as a new block. In the consequence this view lets vanish the distinction between block and system--with the consequence, that labAlive only provides a class for systems, not for blocks.