3.3 Class Hierarchy

In order to make the labAlive toolbox extendable, all systems which can be used in a wiring are derived from abstract base classes which perform the basic functionalities (see example in figure 1). Table 1 gives a brief extract of the class hierarchy and the distribution of tasks.

Class Performed Functionalities

WiringComponent Layout, i.e. position and size of the graphic display of the wiring component (canvas) within the layout grid

System Connection of systems and wires,
Initialisation and signalling routines,
Provide a set of different standard canvas for displaying,
Handle user interaction (open property window when clicked on its canvas, show properties and accept user changes of values)

AnalogSystem Allocate memory (a field of Analogsignal) for the system states

FIR Simulation routine (step)

SineSource Initial simulation routine (startstep)

Table 1: Classes used in the example and their functionalities

**Table 1:** Classes used in the example and their functionalities
Class	Performed Functionalities
WiringComponent	Layout, i.e. position and size of the graphic display of the wiring component (canvas) within the layout grid
System	Connection of systems and wires, Initialisation and signalling routines, Provide a set of different standard canvas for displaying, Handle user interaction (open property window when clicked on its canvas, show properties and accept user changes of values)
AnalogSystem	Allocate memory (a field of Analogsignal) for the system states
FIR	Simulation routine (step)
SineSource	Initial simulation routine (startstep)

The basic programming of a new system requires only an implementation of the simulation routine, i.e. calculation of the output signal. The essential functions concerning simulation, display and user interaction are provided by the base classes, but can be overridden by customized routines, which e.g. provide a specific canvas for displaying (see section 4.2).