For illustration purposes throughout this chapter (as well as Chapter 13 on topic maps and semantic networks), a genealogical chart (that is, a family tree) is used to explain the concepts presented. Family trees express relationships between people, whereas topic maps, RDF, and semantic networks describe relationships between data items. Knowledge can be inferred by examining and compiling the relationships between the nodes of any of these networks. For example, in Figure 12-1, Eric, Becky, and Dawn are siblings because they share the same parents. Keri and Olivia are cousins because their parents are siblings. Cara is Carmen's grandparent because Carmen's parent is Cara's child.