A dataset is any collection of information that is the target of analysis. The four basic dataset types are tables, networks, fields, and geometry. Other ways to group items together include clusters, sets, and lists. In real-world situations, complex combinations of these basic types are common. Many datasets come in the form of tables that are made up of rows and columns, a familiar form to anybody who has used a spreadsheet. The dataset type of networks is well suited for specifying that there is some kind of relationship between two or more items. An item in a network is often called a node. A link is a relation between two items. For example, in an articulated social network the nodes are people, and links mean friendship. In a gene interaction network, the nodes are genes, and links between them mean that these genes have been observed to interact with each other.