Systems Analysis and Synthesis

2.8. SUMMARY

It should be obvious to the reader that there are strong connections between the various ideas presented in this chapter. Relations are just special kinds of sets. Although some relations are best defined by enumeration (such as who is the parent of whom), others are better defined by predicate calculus expressions. Graphs are a way of representing relations that is better suited to the human visual system than matrices or lists of pairs. Labelled graphs are often a superimposition of several simpler graphs.

For example, if R={x↦y∣P(x,y)}, the ideas of relation, graph, and predicate are connected as follows:

xRy⇔x↦Ry⇔P(x,y)

Finally, ...