PROPERTIES OF SOCIAL NETWORKS
A social network can be defined as any bounded set of connected social units. This definition highlights three important characteristics of social networks. First, networks have boundaries. That is, some criterion exists to determine membership in the network. In some networks, such as family systems, friendship groups, and work teams, boundaries are relatively straightforward and easy to define. But social networks are also presumed to be embedded in larger social systems. Therefore, it is sometimes difficult to distinguish between a network and its broader social context. The definition of boundaries is a critical first step toward the study of social networks.
The second key element of the definition is "connectedness" in social networks. To be part of a social network, each member must have either actual or potential links to at least one other member of the network. These links may be direct or indirect. While some members may be peripheral in the network or almost completely isolated, each one must somehow be connected to other members if it is to be considered part of the network.
The third key aspect of this definition is the social unit. Network analysis can be easily applied to a wide range of social units. They can be individuals, as in the case of social support networks. But they can also be social service agencies, social institutions in local communities, or nations in the global economy. In a diverse profession like social work, social network analysis has direct applications for the study of clinical practice, social policy analysis, community organization, and organizational management.
The concept of social network embodies a complex set of social phenomena and studies of social networks have examined a diverse set of properties. As a way of summarizing these properties, we have classified them into two major categories: relational properties and structural properties. Table 1 presents a brief summary of the properties under these two dimensions.
Relational properties focus on the content of the relationship between network members and on the form of these relationships. Studies of relational properties typically seek to understand why a network exists and to ascertain the functions performed by the relations among the members. Two aspects of relational properties have been studied: transaction content, and the nature of relationships. Transaction content refers to what flows or what is exchanged in networks. Four basic types of exchange content have been identified: resources, information, influence, and social support. The nature of relationships refers to the qualities inherent in the relationship between members of the network.
While relational properties deal with the content of relations, structural properties describe the way members fit together to form social networks. Structural characteristics of networks can be divided into three levels of analysis: individual members, subgroups, and total networks. Measures of individual members describe differences among their connections to other members of the network. These differences can be used to identify individual roles in the network, such as star, liaison, bridge, and gatekeeper (Tichy and Fombrun, 1979; Paulson, 1985). Measures with subgroups as the unit of analysis represent the structural characteristics of clusters within the total network. Most social networks contain areas of concentration that have more linkages or connections between members than others. These concentrations are examined as clusters. Measures used at this level describe both the structural characteristics of the sub-group itself, and how the subgroup fits into the total network.